Dear Uncle Fester-looking ex co-worker:  I regret expediting your firing. I realize now what a  mistake it was to quietly push your huge Easy buttons until you spazzed out with your weird temper tantrums and then stand by as our manager documented every episode. 
Oh you deserved to get canned alright. Your incompetence was only matched by your arrogance and failed attempts to bullshit customers. But the thing is, you made me look oh so very professional, knowledgeable and superior that all i had to do is show up each day to be golden.  And oh yeah it was kinda hilarious watching the stubby little guy get all redfaced and nonsensical simply because he couldnt go to lunch on time. But now you are gone. You completed me man!