Tyrannosaurus Rex

 (aka T-Rex or T. Rex) is a giant dinosaur appearing in multitude of Tomb Raider games.

Tactics
The T-Rex has many ways to kill Lara, so it's really a death-wish to stay near it.

Tomb Raider 1/Anniversary
There's a cave in the valley where you can take shelter and shoot him at the same time. It's the best way to kill it. You can also  use the shotgun from close range to make quick work of it. Another way is to equip the pistols as soon as possible, and back flip and shoot until it's death.

This battle was reincarnated in Tomb Raider Anniversary, the re-imagining of the classic original Tomb Raider game. However, the tactics are different this time especially with the introduction of the adrenaline dodge. Before the fight there will be an quick-time event so follow the button presses. Then the real battle begins. You must endlessly shoot it. Once it gets enraged stop shooting but keep your guns drawn and go near one of the spiked rocks. When he attempts to attack you, dodge to the left or right and when the two red reticules overlap immediately shoot! You can say that your adrenaline dodge attack is successful if the T. Rex hits the spiked rocks. This takes away one-third of the dinosaur's health meter. This means that it takes three spiked rocks to kill the T. Rex. Then another quick-time event ensues so just follow the button presses.

Tomb Raider 2
There are two at the same time! To safely kill them, stay in the little hole where the third secret was.

Tomb Raider 3
Right after you grab the key that was in his nest, he appears. Run as fast as you can to the small cave with a lever (it is right at the side of the slope that you used to get down) to kill him from a distance. Staying in the deep water is also a safe way to kill him.

Lara Croft: Relic Run
A T-Rex appears as a boss of Cambodia's Jungle Temple. Easiest way to kill it, is with maxed-out Crossbow. If you are fast enough with the clicking, you can take out T-Rex with two encounters (gets tougher after every kill).

Appearances

 * The Lost Valley(1)
 * The Great Wall(2)
 * Nightmare in Vegas (2)
 * Crash Site (1)
 * Peru - The Lost Valley (1)
 * Jungle Temple (2)

Trivia

 * The T. Rex in TRA, as the commentary states, is probably much larger than a real Tyrannosaurus Rex would be.
 * There's a T. Rex trophy inside the treasure room in Tomb Raider III.