Executioner lets you stealth attack heavy Freakers such as Breakers and Reachers, and kill them or large animals when you break their grapple. It is a Tier 5 Melee skill and one of the last you will unlock in the tree.
It is worth it once you reach Tier 5, mainly for Breakers and bears. Most players get there in the late game.
Escape Artist and Thief In The Night. Quieter movement makes it easier to get behind a Breaker unseen.
Breakers usually travel with Swarmers. Thin out the escort first, or a stealth attempt turns into a brawl.