In Mafia III, using your melee attacks on enemies is, hands down, the best way to take them out. First off, it’s worth noting that there are two ‘types’ of melee attack executions in the game: if you’re able to melee an enemy while undetected, your execution will be more subtle and silent. However, attacking them when they’re already aware of your presence will allow Lincoln to perform various execution moves to take them out.
For example, if you sneak up on an enemy and hit the melee button from behind, most of the time you’ll choke them to death. You can also use the melee attack from behind cover, and Lincoln will grab hold of the enemy and take them out behind cover. If you use the melee attack in the heat of battle, Lincoln will perform a cool execution move where he does a suplex and completely decimates your helpless foe. In certain situations, he might also make use of environmental objects to execute enemies too.
To do a brutal takedown with your knife, hold the melee button, and release it once the bar hits the highlighted area in the cursor.
It’s good to rely on your melee attacks as you can run out of ammo pretty easily in Mafia III. If an enemy is near you, consider taking them out with an execution/melee takedown instead of using your gun.