The Plague Ogryn in Darktide is large, cumbersome monster that does high damage at close quarters. You can dodge its attacks if you are quick, but this is high risk as you will take a lot of damage if hit. It's a good idea to learn the attack patterns of the boss before attempting to do this. If you're unsure, then just play defensively when the Ogryn is attacking you (blocking and dodging) and then switch to attacking when he turns to focus on someone else.
Plague Ogryn Monstrosity in Darktide