Was Snape stronger than Bellatrix?
In the end, Snape's greatest power was his ability to love in such a pure form that no Dark Lord could ever defeat him. Bellatrix had a different kind of love for Voldemort, in that she was maddeningly obsessed with him.
Can Snape beat Voldemort in a duel?
Moreover, Snape can easily resist Voldemort's Legilimens attempts like he has done so many times to hide his allegiance with Dumbledore. ... Snape's no slouch and could have easily use his hidden knowledge and spells against Voldemort in order to win especially if he has a cause to fight for. He might even win, who knows.