Cowardly Boss

A boss that the party fights, that then randomly runs after taking a certain amount of damage, forcing you to have to hunt that boss down and fight them again. Thankfully, most followers of this trope will retain the damage they took in the previous fight.

Compare the Recurring Boss, who runs as a matter of the storyline. See also Get Back Here Boss.

Action Adventure

 * The Master Stalfos of the fifth dungeon in The Legend of Zelda Links Awakening.
 * The worm boss at the beginning of Metroid: Zero Mission.
 * Koji Shindo in Yakuza 2 (Ryu ga Gotoku 2) uses a katana in order to fight you, but runs after taking set amounts of damage. You eventually corner him in a Japanese courtyard, where Yayoi throws you a sword for the Blade Lock duel to the finish.
 * Skull Kid in The Legend of Zelda Twilight Princess. Although, in this case, he was actually trying to lead you somewhere.

Action Game

 * The Lego Star Wars/Indiana Jones/Batman games feature lots of examples of this. Expect to do some mild platforming or puzzle solving in between each hit on a boss.
 * Mahasti of Prince of Persia: The Two Thrones.
 * In the NES version of Jaws, the titular shark will sometimes disappear after you wound it forcing you to track it down again. Often, it will have healed forcing you to start over before getting to the actual attempt to kill it. Possibly a subversion since the shark doesn't run away as much as the timer for attacking expires.

Beat'Em Up

 * The fight with Dr. Mueller in Splatterhouse 2 is of this kind. He dies in one hit, but you got to chase him down his lab while he runs away throwing at you potassium bombs and Invincible Minor Minions and trying to avoid some explosive traps.

Fighting Game

 * WWE SmackDown vs. Raw 2009's Road to WrestleMania mode actually has one of these - in Chris Jericho's story mode, he is being harassed by a masked man who will repeatedly escape by some way or another every time Jericho has the chance to get his hands on him he escapes. Depending on what choice you make at a crucial point, you either  or
 * Ganryu, Paul, and Xiaoyu in the Campaign Scenario of Tekken 6.

MMOs

 * In City of Heroes, some bosses (or at least mission notables) are programmed to run after hitting a certain health threshold, and you're supposed to stop them from running. If they escape (i.e. zone out of the map), you fail the mission, so there's no rematch.
 * The Ghostring in Ragnarok Online can pack quite a wallop. However and rather frustratingly for players, when its hitpoints drop below a certain threshold, it'll spam teleports and move randomly around the map in an attempt to avoid the player (to be precise: 50% chance of teleporting every time it attacks).
 * The Stonecore, one of the new 5-man instances in World of Warcraft Cataclysm, has a gnome that is this and a Bait and Switch Boss. You find him at the beginning of the instance with a group of mooks, and when he takes some damage he flees to another group of mooks further in. Repeat twice more, and he finally takes a stand with a huge crowd of mooks and begins charging his ultimate spell of doom... when a gigantic gyreworm smashes through the cavern wall, wiping out the gnome and his backup in one fell swoop.

Platform Game

 * The second part of the boss fight with the giant possessed tree in Drawn to Life consists entirely of trying to track down a small, shadowy lizard thing that leaps erratically between the platforms of the area so you can shoot him. He dies in three hits and doesn't even try to attack; however, he is exceptionally annoying to keep track of and there are bunches shadowy tentacles scattered about the area that lash out at you if you get too close.
 * The Hulking Lungfish in Psychonauts is fought in four sections; in between those sections, it runs away from you, pulling its underwater air-bubble along with it. Raz isn't such a strong swimmer, so you have to chase her while staying within the bubble. Guess which part of the boss is more difficult?
 * Dr. Nefarious in Ratchet and Clank Up Your Arsenal combines this with I Surrender, Suckers.
 * The Final Boss of Kid Niki: Radical Ninja.

Real Time Strategy

 * Asdrubael Vect in Dawn of War: Soulstorm when assaulting the Dark Eldar stronghold. He often attempts to solo your base within his Pimpmobile Dais of Destruction, but when taken fairly minor damage he will scream to be taken back for repairs and repeat the process. The player can potentially tech up enough so that the next time he pays a visit you can unleash your own wave of destruction and hopefully blow him up before he returns to the base, thereby winning the battle and beating the Dark Eldar.
 * Sometimes he gets stuck between his own units horrible pathfinding and the side of a cliff.
 * And then there's things like the Tau Barracuda, which are pretty good hunters.

Role-Playing Game

 * Ultimate Weapon in Final Fantasy VII.
 * Deathgaze (also known as Doom Gaze in the SNES version) in Final Fantasy VI and his cameo in Final Fantasy IV: The After Years.
 * Kefka is one of these early in the game, when he's just a funny clown. Later on, it's the protagonists who run from him.
 * The Jumbo Cactar in Final Fantasy VIII. This rather annoying boss has a ton of HP and can kill a character in one shot regardless of stats. After a certain point, it thinks about running away. If it does, you have to do the whole fight from the beginning.
 * The Legendary Dogs/Cats/Gerbils in Pokémon Gold and Silver, Latios/Latias in Pokémon Ruby and Sapphire, and Mesprit and Cresselia in Pokémon Diamond and Pearl, Unless you have a Pokemon that knows a move like Mean Look to prevent it.
 * And in Platinum, Mesprit, Cresselia, and the Legendary birds, Moltres, Articuno, and Zapdos, all fit this trope.
 * Pokémon Black and White gives us Tornadus and Thundurus. Unlike the rest, you can use the weather to determine their whereabouts. If it's raining like mad in your area, get your Repels and Master Ball ready...
 * They aren't bosses, but in Pokémon Mystery Dungeon, Pokemon with the ability 'Run Away' will flee if they're hurt too much. (Even your own Pokemon do this, unless they're the head of the party.)
 * Darth Malak in Knights of the Old Republic does this - twice.
 * Then there's the final boss fight, when every time you do a certain amount of damage to him, he runs off and sucks a Jedi captive's life energy out, completely healing himself. You can't attack him while he's running, but you can either kill the Jedi, allowing them to become one with the Force (they're basically dead anyway,) or suck their life out yourself.
 * Not exactly a boss, but the ??? (yes, that's its name) from Dungeon Siege 2.
 * The Greenbottle Fly in Breath of Fire 2 is a minor example: you only fight him twice, but in between, he leads you on a chase through two boss fights and a minefield of enemies.
 * Ozzie from Chrono Trigger runs across the bridge, then animates the dead bodies into a giant skeleton to stall you. Then later in Magus' castle, he only confronts you in the second-to-last room, meaning you've defeated literally everything in Magus Castle except for Ozzie and Magus. And then Ozzie casts an impenetrable barrier on himself.
 * Most boss monsters in the Monster Hunter series will either run, dig, swim or fly to another area after you've damaged them enough, and to finish the job you'll have to find them again. Marking them with a paintball, paint shot or paint-coated arrow will save you a lot of time figuring out exactly where they flee to.
 * Not really a boss (like many other things on this page), but a really strong enemy. The Amazee Dayzee in the Paper Mario games will run away as soon as it can. Made worse by the fact that it's super rare, and in the first game, it's the only thing that will give you exp at high levels (aside from Dry Bones, but those only yield Star Points if you burn them to ashes.) In Super Paper Mario, it'll even jump into bottomless pits to escape you.
 * Popple in Mario & Luigi: Superstar Saga runs away if you defeat his partner first.
 * Earlier, in Super Mario RPG, each showdown with Croco sends you on a wild chase after him. The first time, you have to catch him by surprise thrice. The second time he's better-prepared, and sets traps for you before scurrying off.
 * Several bosses in Dragon Age Origins vanish and reappear in different locations after taking damage. The Arcane Horror miniboss in the Brecilian Ruins teleports whenever a character gets near it and leaves a lightning storm in its wake. The Giant Spider Queen in Ortan Thaig will retreat back to the ceilng after webbing you up and summons a couple of its offspring. Both pale in comparison to the Archdemon. He flies to different locations after taking enough damage while Darkspawn reinforcements hassle you. At one point he lands in a spot that melee characters can't reach (so if your party is a melee-centric one, you're in trouble), leaving him free to spam his ranged Spirit attacks.
 * The latter case is only a problem if you don't have a rogue who can keep the ballistae working. If you do, then you can just pelt him with ballistae bolts until he charges back into the fight.
 * The Mega Man X Command Mission gives us the rotund, untrustworthy, power-hungry would-be traitor Botos. He tries to attack X and crew, goes down like a chump, then runs for the hills a good couple of times, forcing you to waste time and energy chasing him down. Frustratingly, the game doesn't even let the player actually beat him properly.
 * The first battle with a Red Cape in Devil Summoner: Raidou Kuzunoha vs. the Soulless Army is this. In fact, it'll keep running away, until you block its path with a car.
 * Tielle in Recettear is fought in three stages, with her running away and hiding among piles of cardboard boxes after you deal enough damage to her.
 * Omen Deng in Alpha Protocol. First he leads you on a chase/shoot-out through an intricate construction scaffolding, disappearing every time he takes a certain amount of damage (and leaving behind Mooks armed with assault rifles). When you finally get him alone, his M.O. is to hide behind a pillar, take some shots at you from cover, run off and disappear, run back to you and beat the snot out of you in melee, then run off and disappear again. Rinse and repeat until one of you is dead.

Shoot'Em Up

 * The most cowardly boss ever is the penultimate Golem-style boss from Lylat Wars on the easy route. He runs away from you constantly, fleeing down an endless corridor, never attacking you in any way. But he conjures pillars out of the walls and floors which you have to avoid - flying your Arwing in to them really hurts. He makes a comeback in Command, along with smaller forms that pretty much act the same.

Third-Person Shooter

 * Jerry Ying from Stranglehold, in keeping with his Dirty Coward persona after  at the Chicago History Museum, runs off after losing only a quarter of his health in his first major clash with you and yelling "This isn't over yet, Tequila!" You then have to kill your way through a good number of more mooks before finally cornering him in the stage's final showdown.