你不是什么学霸而是人渣
[nĭ bù shì shén me xué bà ér shì rén zhā]
The meaning of this username can be quite harsh. Literally, it means 'You are not a study god but an evil person.' It could be a provocative self-deprecation, which means that while someone might want others to believe they are smart, in reality, he or she feels they aren't. And 'study god' here refers to very studious students.