[quote=mumbai_masti]Well if it was voldy then he will certainly not go against him (he was a former death eater) and also in OOF his worst nightmares were consists of sirius and james...[/quote]
It was his worst memory, but that doesn't mean that he was actually scared of them. Eg: Harry's worst memories would include the Dursleys, the humiliations by Snape and the Slytherins, but he is not scared of them - he's scared of Dementors.
Though it would be very interesting if Sirius or James ended up being Snape's Boggart - and really funny too. 😆
I dont think Snape fears Voldy either...Otherwise he wouldn't have dared to leave the Death Eaters.
Perhaps his father???? The hooked-nosed man shouting at a woman (Snape's mom?) while a small boy (Snape) cried in the corner???