Snuff Out is mediocre here: it can hit their blue creatures like Spellstutter Sprite, Faerie Seer, Augur of Bolas, and Ninja of the Deep Hours, but those are mostly small utility bodies that already replaced themselves. It can't target the black creatures that matter most, namely Baleful Strix (blue-black), Thorn of the Black Rose, and Mukotai Ambusher. Paying 4 life into a control deck full of removal and card advantage is also a bad trade. Mesmeric Fiend proactively strips their best card from hand, which is huge against a deck that wants to sit back and draw cards. Try to resolve it when they are tapped out or short on Counterspell mana. Tragic Slip is efficient, cheap removal that kills Baleful Strix outright and takes out Thorn of the Black Rose once a creature has died this turn, and it doesn't ask us to overextend. Sadistic Glee and Rite of Consumption are too cute against a deck with ample removal and Counterspell backup.