Cornered Rattlesnake

"Put the army in the face of death where there is no escape and they will not flee or be afraid - there is nothing they cannot achieve."

—Sun Tzu adressing this trope

The Cornered Rattlesnake is when a character or a faction is pressured to the breaking point. Another group or the 'Big Bad' will bully or threaten the weaker 'rattlesnake' until the weaker person fights back. Sometimes the 'weaker' group is actually surprisingly powerful, but the bully underestimated their abilities. Having the rattlesnake 'bite back' is something the big bad normally didn't intend or anticipate, and so he will face the consequences.

Sometimes a Cornered Rattlesnake will be given assistance from the enemies of the 'big bad bullies', and so will begin to be able to defend itself. The 'big bad's' cruel actions could actually make their allies turn towards the 'rattlesnake's' side.

The phrase refers to the real life scenario of if a person were to corner a rattlesnake. The human can easily choose to retreat, but instead tries to kill the rattlesnake. Cornered, the rattlesnake would defend itself. This trope doesn't require the rattlesnake to win, as it is possible to kill the snake, but being bitten is highly likely.

Sometimes this is a response to a No-Holds-Barred Beatdown, Hopeless Boss Fight or Curb Stomp Battle.

This isn't Bullying a Dragon, as the cornered rattlesnake appears, at first, to be physically weaker or a huge coward and only reacts in self defense.

Examples of Cornered Rattlesnake include:

Anime and Manga

A common situation of the cornered rattlesnakes is that the hero is forced to use a risky move or a Heroic Sacrifice to defeat his enemy.

Film

In Toy Story, Sid's toys have been brutalized by Sid, who sadistically enjoys destroying, damaging and disfiguring his toys. The toys risk being exposed as living creatures, but are able to scare Sid into respecting them.
In Iron Giant, The Giant is attacked by the US military. This leads the robot to engage into a 'battle mode' where he uses giant alien weapons to destroy almost everything in sight. The military itself becomes the Cornered Rattlesnake now and arms a nuclear missile to destroy The Giant, even at the risk of killing everyone in town.
In the Dark Knight, the gangs of Gotham are forced to hire the Joker as the police and Batman are overwhelming their gangs. This leads to Joker blowing up many buildings and threatening or massacring dozens of people.

Video Games

Painwheel from Skullgirls has been experimented on, brainwashed and mutilated by Valentine's labs. Her scarred and deformed body makes it impossible to live a normal life, even her family cannot recognize her and mistake her as a murderous monster. Painwheel was once a normal girly teenager, but now is a feral and violent fighter. Valentine's greatest weapon is now her biggest threat.
Chell, from Portal, is forced to destroy GLaDOS, who is forcing Chell to go through dangerous test chambers and even attempted to kill Chell by dragging her into a fire. Otherwise Chell is just a normal person, while GLaDOS is a giant robot that can fire rockets, summon turrets and poison rooms with neurotoxin.

Western Animation

In the first episode of Batman Beyond, Bruce's Batman is too old to fight against the goons. One of them is about to beat Batman with a pipe, forcing Batman to use a gun to win. Batman, who hates guns, decides he needs to retire in his old age so he wouldn't be in this situation again.
My Little Pony: Friendship Is Magic: Fluttershy protects her friends by actually [[Beyond the Impossible|staring

Real Life

Vietnam during the Vietnam War.
Many revolutions were formed by militias of citizens, who were too pressured by their governments to survive without rebelling.
Unfortunately, there are many examples of people who are driven to suicide, murder or murder-suicide from bullying, threats and other attacks.
Carpenter ants can self-destruct, spreading their poisonous guts over their enemies.
Rattlesnakes, duh.
Skunks are normally peaceful creatures, but will spray predators with a smelly liquid if threatened.