Family Guy easily. Everything after the point where Brian was killed off and revived is basically a 'Kill me' cry at this point with how sadistic it's gotten since that point; it's like that show is begging to be put out of its misery.

Pokemon doesn't count because they recently retired Ash and brought on a new lead character in his place, and they're actually trying to branch out more lately with spinoffs such as Pokemon Concierge, which that spinoff is adorable from what little I've seen of it, btw.

Spongebob also needs to end just out of respect for its dead creator. Like, if Nick had any respect for Hillenberg's wishes, which if I'm remembering this right, he wanted no spinoffs of Spongebob, they should've just ended that show after he died and left it alone from there, what they're doing with that IP is basically pissing on the guy's grave.

Edit: Going back to Pokemon spinoffs, I'd love to see the existence of sort of a Pokemon 'Busytown' although that's not something I'd actively seek out, because that would be ridiculously adorable as a concept, ditto for taking 'Pokemon Art Academy' and turning it into sort of an animated 'Art Attack' counterpart, how Nintendo didn't try that, I will never know as it would've been genius on their part.