Adrenaline Mode is a gameplay feature in the Tomb Raider series, specifically appearing in Legend Timeline.
Tomb Raider: Legend Edit
The adrenaline mode takes the form of the Aerial attack.
Lara must lock onto an enemy, and jump on them, this will stagger them and put the game into slow motion. This will give Lara an oppourtunity to kill the enemy, and any surrounding enemies around them. There is no limit to how many times it can be used, and simply relies on being able to get close enough to an enemy in order to do so.
Tomb Raider: Anniversary Edit
Adrenaline Mode takes the form of the Adrenaline Dodge Headshot. It is activated by attacking enemies, and raising their rage meter. When it's full a flash will appear above their head and they will charge, in order to attack Lara. The attack must be dodged at the last second, the game will then go into slow motion, and two target reticles, will slow move towards the enemies head. Once they come together, giving the opportunity, for a one hit kill, or in the case of bosses, inflict massive damage.
Tomb Raider: Underworld Edit
The Adrenaline system has been tweaked, allowing Adrenaline to be turned on and off, allowing for better reaction time, and give player s a chance to dodge enemies.
The Andrenaline Headshot now functions similarly to the Aerial attack, instead of relying on the enemies rage meter. However the Adrenaline bar must be filled to use it. Lara must lock onto the enemy, and grapple them, causing her to jump into the air, an aiming reticle will appear, which must be guided over the enemies head, to finish them off.