Roaring Rampage of Romance

Alice loves Bob, and Bob loves Alice. But then, it would be too easy if it was this easy: for some reason, Alice and Bob cannot be left to live happy together. Sometimes, this leads to Love Makes You Crazy, when Bob stops acting rationally to stay with Alice. Sometimes, Bob decides to take care of this annoying guy who claims he wants just to be Alice's friend. Sometimes, Alice decides to torture and murder all of Bob's female friends so he won't be distracted by all these, well, You Know What I Mean... Sometimes, Bob coldly decides to sacrifice his Nakama to save Alice.

This is none of these situations. This is when Alice and Bob stay, most of the time, level headed and genuinely try their best to be together, and notwithstanding their success or failure, the Collateral Damage is at least 147 deaths, the destruction of three cities, and maybe even the Endofthe World As We Know It. Even if it can involve some irrationality (after all, Love Makes You Crazy or sometimes evil), it's not the characters' flaws, but the circumstances that force the couple to go to extreme length to be together. Or, even worse, they didn't even realize what they were doing, and the couple's stubborn insistence on being together results in an unintended ripple effect of death and destruction. In short, this trope is not about characterization, it is about the effects of a relationship on the story and the setting.

Can involve Love Makes You Evil or Love Makes You Crazy. This is an inversion of Destructo-Nookie where the rampage part involves only the couple, and usually does not leave the bedroom.

This is a trope about how romance can be really, really destructive. That's just what happens when you place the huge power of love into the hands of someone in love. They become irrational, and mad with power. Expect at least one case of Murder the Hypotenuse, especially if there is a Yandere involved.

The Trope Namer is Love Actually, by way of its Tagline, though it's not an example.

Related to Love Makes You Evil and Love Makes You Crazy. Also related to Destructo-Nookie. Sometimes caused by Always Save the Girl.

Anime & Manga

 * Mirai Nikki: By the end of the series,
 * Rebuild of Evangelion: Shinji triggers The End of the World As We Know It just to save Rei.
 * in Tsubasa Reservoir Chronicle,
 * Also, in X1999, Kamui's wish to get  back even if it causes  and the rest of the world harm. Can also be said for a lot of other characters.
 * Umineko no Naku Koro Ni: Kinzo and Beatrice

Film

 * A lot of people wouldn't had died if Anakin Skywalker never fell in love with Padme Amidala.

Literature

 * This is the basic premise of Wuthering Heights.

Live-Action TV

 * This is one of the themes of Buffy the Vampire Slayer.

Theatre

 * Romeo and Juliet's romance causes six deaths. 1: Mercutio: Killed defending Romeo. 2: Tybalt: Killed by Romeo. 3 Romeo's mother: Died of sadness because of Romeo's banishment. 4: Paris: Killed by Romeo. 5: Romeo: Killed by Romeo. 6: Juliet: Killed herself because Romeo did.
 * Love rarely ends happily in the operas of Richard Wagner. (Of course, what did you expect in an opera -- a happy ending?) It causes Senta to jump off a cliff, Elisabeth and Heinrich apparently just to keel over, Elsa to betray Lohengrin and then to keel over, Siegmund to commit adultery with his own sister and be killed by her husband (she dies in childbirth), Gutrune to drug Siegfried into loving her so that his wife kills him and then burns herself to death, and Tristan to get fatally wounded while messing around with Isolde, the king's wife, who then herself keels over. Only Walther and Eva seem to end up well.

Tropes

 * Outlaw Couple.

Video Games

 * In Super Mario Bros Bowser and Mario both love Princess Peach. Bowser kidnaps PP, and Mario saves her. Between them, they cause the deaths of countless koopas, goombas, and other minions that did nothing wrong.
 * Gwendolyn and Oswald of Odin Sphere, which is very, very loosely based on Wagner's Der Ring der Nibelungen. They meet on a battlefield and between the two of them have stormed cities and literally gone to hell and back for each other. Without even knowing how the other feels.