Lol you could say something like this. If you were willing to diss your coworkers too haha.
"Hey Mr. (boss's name).
I just wanted to let you know, that these past few (allotted time as an employee) have literally been the worst of all the (pluralized allotted time) of my life. Your incompetent and almost laughable leadership over this socially malignant assortment of morons continues to baffle me.
I respectfully resign, noting that you are a very unattractive human being. Each passing day over the past few weeks have become a chore, as looking at you seems to accelerate the small tumor growing at the base of my skull, which also is a direct cause of your appearance. Even now, i strain to be in the presence of such an embarrassment to the human race.
My resignation should come nothing short of expected. The Reapers are coming, and I am the last thing that stands between the survival of all species in the galaxy, and total extinction. I cannot afford... oh lord, I think I'm starting to smell you. (imitate gagging, then leave)."
Or something like that haha