issh is the gangsta way of saying shit

Marginalized Orientations, Gender identities, And Intersex. it’s meant to be an all inclusive umbrella term for asexuals, homosexuals, multisexuals, trans people, and intersex people. Alternative to LGBTQIAP+
Alternative to MOGII, easier to pronounce.

i suck so hard (you say you do, but actually you suck)

Issh is short for issue.
You've got something you deserve coming to you.