"..that guy is just a washout"
Washout, from M-W
- one that fails to measure up : failure: as
a. one who fails in a course of training or study
b. an unsuccessful enterprise or undertaking
"He was a washout as a professional golfer"
"The team lost so many games that the season was a total washout."
"Yesterday's game was a washout."
To add more emphasis, you may say:
"..that guy is a colossal washout"
more informal synonyms: flop, dud, non-starter, no-hoper, lead balloon, fail, clinker, damp squib, lemon, loser, dead loss, dead duck
Another suggestion is:
Non-achiever, from ODO
A person who is unsuccessful, especially in the attainment of educational goals:
"all his life he’s never had praise but been told he’s a non-achiever"
After your edit, I have this new suggestion:
Cupcake, from ODO
2.1 A weak or effeminate man.
I'm not sure if this term is popular, though.