John Cena's marriage-ending home remodel just got worse -- 'cause a construction worker claims he was so badly injured on Cena's watch ... it left him unable to work.
The construction worker, Dale Ducharme, is suing the wrestler (but not John's ex) ... claiming he fell off a crappy scaffolding provided by the wrestler back in '10 during the remodel of Cena's Florida home.
Ducharme says the scaffolding was defective or damaged ... and it was the ex-WWE champ's responsibility to make sure the equipment was safe.
Ducharme wants more than $15k to cover the pain, disfigurement, loss of enjoyment of life, yada yada yada.
A rep for Cena had no comment.
Check out the clip below -- it's not an actual re-creation ... but you get the idea.