I'm told cheaters run rampant in Dark Souls. Never seen one, and that's one of my favorite games of all time. I've lost invasions many a time, and people have used advanced magic, endgame weapons, all that on me.
Doesn't mean they cheated, new game plus is a thing, and the summoning levels (and now weapon matchmaking) are easily gamed to allow you to invade people less well-equipped than you are.
I've seen videos of actual cheaters, who hit you with a homing soulmass and it breaks all your equipped weapons and armor. Or they never run out of stamina. Or whatever. But I've never seen one in person, and I've wasted far too much of my life on that game.
Some games have lots of cheaters. Some don't have any.