I think you might be way overestimating a guy that sings crappy music for a living compared to a guy that trains to fight every day.
If it was someone with no boxing experience whatsoever then I would agree that Colby would win.
A cursory glance at 50 cents boxing though would show that he does have some experience. He’s far from being any good, but he at least moves correctly, and punches with decent form.
To beat him with one hand tied behind your back you have to either be much, much better than him (as in a decent boxer level good) or have the ability to one punch KO him. I’ve haven’t seen anything in Colby to suggest he has either.
So no, my thoughts aren’t based on 50 cent being good, they’re based on Colby not being so much better than him that he can compensate for such a drastic handicap. Think about movement for a second - what happens if they take away Colby’s right hand and 50 Cent simply refuses to do anything but circle to his left (towards Colby’s non-existent right) and consistently for a jab in his unprotected face?