Enders: I can't work it out, is Yusef good or bad?

He's not good, he's evil! All those evil smiles make it obvious his intention is to split Masood and Zainab up. He likes winding Masood up and he's trying to cause rifts like with Afia's engagement ring, writing the cheque for Zainab, telling Zainab that Syed was critical in hospital etc. He's clever though as no one can really see through it as he's masking it by trying to do 'good' deeds.