READ THE COMMENTS!!!11ONEONE
After some consideration (And over-analyzing DOOM 2016) we have found that the Doom Slayer could most likely be able to defeat Optimus Prime easily. Yes, we did acknowledge that Doom Guy is well, a guy. But, he is also fueled by pure rage and has multiple weapons much like Optimus Prime. We just don't think Optimus could be able to survive the Doom Slayer, especially when you put into context the other things the Doom Slayer has defeated (such as the Icon of Sin from Doom Eternal). Apologies if this wasn't the outcome you wanted :)