After finishing game on normal you will be able to choose character costumes.
Parker costume used by him in ship levels posses big axe. That axe can simply one shot Hunters.
Hunters are only enemies in Terragrigia so basicly you can melee trough whole level without shooting one bullet.

Remeber however - befor starting Terragrigia level you must go back to menu and choose his first costume


In that way both episodes in Terragrigia will be much more easier.