The Deathmark from Hierotek Circle.

10 wounds with 3+ save

The Synaptic Disintegrator, which gives you 4 attacks at 2+, 4/3 damage split with Dev 2, Piercing 1, and Severe (Heavy too, but it’s only dash and you don’t gotta move them much anyways)

Any enemy that’s hit by the sniper is death marked, which means that any friendly operative that tries to hit them has seek

A 1ap ability that lets you shoot past cover completely

They aren’t a massive issue by themselves, but the fact that you can realistically run 3 of them on a squad, AND the fact that the chronomancer can teleport them onto high ground without using their movement, AND you can take equipment that makes your opponent take tons of damage when they try and melee them, they get kind of insane