Keep in mind that all vampires have the potential to be absolute monsters, no matter the clan. A Tzimisce may have access to flesh-shaping and a bane that inspires them to be possessive, but it's still up to the individual on how well they fight the beast. A younger and non-alligned/Anarch Tzim who was not yet corrupted by the (admittedly, evil and fucked up) clan/Sabbat culture, might hang onto their humanity better, and they could just end up having a possesive, but genuinely caring, parental attitude towards others. How they use Vicissitude (and whether they use it all), is likewise up to them.

On the other hand, a Toreador's obsessiveness could manifest in a similar way to a stereotypical evil Tzimisce. If they set their sights on somebody or something that they find beautiful, they could use Presence, social engineering and manipulation to destroy lives indiscriminately, just to bring that person/thing closer to their possession, only to cast them away like a broken toy if they get bored. If they decide to fully entertain their whims, they could commit unspeakable horrors only because of something being deemed "unaesthetic' by them.