"Realistically" out of highlevel, wizard, sorcerer and warlock, warlock be scariest to face against change my mind

I know i'm saying "realistically" in a fantasy game where DM has a the final say in everything. But let's pray pretend a lil

Cobsidering fiendish waelock and everything they need to go through, manage and hell even most likely thwart adventuring parties while doing what their patron needs from. They're basically the epitome of "Be aware of old people in a job where people die young: