I don't know about you, but the thought of tickling so intense and cruel it permanently breaks a person's mind/will makes me diamonds. The kind of stuff done to indoctrinate the victim into tickle slavery or warp their personality in some way, or just to torture them, with a consequence being they end up scarred or an empty husk inside simply because endless laughter just broke their brain. Darker, permanent stuff is the most goated in my opinion, but the more common example of a tickle session ending with the girl making an ahegao expression and muttering slurred nonsense is also hot, even if they probably would go back to normal after a nap and some hydration. Tickle torturing an unwilling participant into becoming a willing submissive/addicted to the feeling is also crazy good (bonus point if they're broken into tickling others instead, either out of fear of suffering even more tickling themselves, or as a genuine twisted desire after their mind has snapped). And just to keep it separate from the tickle hell thread, let's say the ticklee has to be shown being actually mind broken, so it's not just any tickle hell pic where the idea is their mind would probably snap at some point.