It depends on how you interpret better harse/sarcastic/polite/rude you want to be. Words that come to mind include "Losers, incompetant, rubbish, waste of space, past it, crap, sackable, etc...." It also depends on the context, in the script for a gangster film maybe wasteable?What can one call people who mostly fail or lose on most of projects they undertake? Better words than unlucky or hapless?
Thank you ewie for highlighting my incompetence!And incompetant? I don't know that word.