In the following picture:
I understand the meaning of 傻逼 but what is the "j8" before it?
According to chinaSMACK, j8 is equivalent to 'penis' or any of its vulgar forms:
(rude language hidden behind spoiler, hover over or click to show)
Penis, dick, cock. When used as an adjective, it may mean “cocky”, “arrogant”, or a more generalized “fuck” or “damn”.