When you say "he doesn't fail to disappoint", to me it has a negative meaning as in he always disappoints. But I've heard some people using it as a compliment and in a positive way. So, am I wrong about the meaning or it's the other way around?
For example, Christina said on Voice:
My glam team doesn't fail to disappoint and they took the Monday blues
and turned it into a stunning look any girl would love.