a total wuss; someone who whinges a lot in order to avoid a responsibility
a person with the skill/ ability but lacks the balls/spine to complete a given task.
origin: from the character Peter Petrelli, from the tv series 'Heroes', who had the greatest power but could do nothing with it because he was too scared.
"go get some firewood"
"i can't there's animals out there"
"we're in a reserve park, the most dangerous thing out there are mosquitoes"
"MOSQUITOES! i'm leaving!"
"I can't believe you're so scared of mosquitoes. You're such a petrelli"