The Evil Within 2

Crossing to the Other Side Achievement Guide

This is where you defeat Liam O'Neal, he's armed with a Flamethrower and around the arena are buttons that turn on the sprinklers. You will want to press the button every so often as the area will be burning around you meaning that you will not have as much space to move around.

Best strategy I found was to use the Explosive and Smoke Bolts along with the Sniper Rifle and Shotgun.

Hope this helped.

Just beat him on Nightmare without firing a single shot or being attacked once.

If you run far away enough from him, he'll lose you and return to the biggest room in the boss arena, the room with all the autopsy tables. He'll just slowly walk around looking for you. You can then just tip toe up behind him and sneak attack him over and over.

Took 6 sneak attacks, each time just running back through the small cloth lined corridor after a sneak attack to make him lose me. I was able to sneak attack him in the same spot each time.

Whatever you do, don't destroy his flamethrower tank, as it makes him much, and I mean much harder. He'll never lose sight of you again, and he'll keep up with you forever, as he seems to have infinite stamina, he will almost literally be glued to your back. He also has a stab attack that kills you in one hit even if you have over half health(On Nightmare anyway). So just destroy his tank for the achievement, then reload the checkpoint to do the sneak attacks, if you're on your first run of course. He'll still drop the broken Flamethrower even if you don't destroy his tank.

This does not work as well on Classic, since you won't be able to upgrade your sneaking speed at all. The one time I attempted this on Classic, I was too slow without those upgrades, and he turned and hit me a single time, and since you can't upgrade your health either, it was a one hit kill. So for Classic I'd just recommend the shock bolts and shotgun blasts to his head, over and over. He's really easy that way as well. Plus I had over 425 gunpowder and over 100 herbs(With both the lockers and the shooting range, you'll get massive amounts of both of those on Classic)at that point, so it's not like I was hurting for ammo or health.