HELLDIVERS 2

This one can be done pretty easily on solo. I would recommend using the Flamethrower for this as all your kills will count towards the trophy.

First, make sure you purchase the Flamethrower stratagem if you haven't already. Start up a round solo on any planet against the terminids. I used Heeth, in the Orion Sector on trivial difficulty. Make sure you equip the Flamethrower. Call in the flamethrower stratagem as soon as the round starts and kill any enemies you see with the flamethrower. On trivial difficulty the enemies spawn at a pretty slow rate, so it will likely take around 15-20 minutes to kill enough enemies for the trophy

As soon as you hit 100 kills with the flamethrower, the trophy will pop