Karlach has never ruined the game. The Karlach hate is not appreciated. Frankly it sounds like a bug. And there is absolutely no way Karlach went around to all of the other companions lying about you having sex with her. That just did not happen. I’m sure that Larian would appreciate it if you reported the bug to them.
As to how you can fix it, I mean, the only thing I can think of is restarting from an earlier point in your save. Hopefully other folks can chime in as to whether they are also having this issue. But again, hating on Karlach’s character over what is clearly a bug is not fair or helpful.
Edit: maybe if you went back to an earlier save, and then killed Karlach, it could fix it for you, who knows. Seems like a viable option.
Karlach is a goody goody who doesn't approve of anything you do unless it is getting in her pants. I ignored her on my first play through, mainly because I didn't find her until the eend of act I, and on my second I wanted her, Wull, Minthara and Astrion, but upon reaching ActII I screwed something up and Minthara wasn't there so I started a new Dark Urge, killed Wyll and Karlach so I could raid the druid temple, then slept with Minthara and then Ressuracted Wyll and Karlach, and then somewhere a chain of something happened because now everyone thinks I boned Karlach and I can't even do that because all the tieflings are dead and she'll burn people...so frustrating...also, the slayer form sucks, even after patch 4!
