He doesn't qualify as a coward. He was willing to get all his drones to fire on Spider-Man despite the risk of himself getting shot. As for showing fear when his drones are getting destroyed, that's self-preservation kicking in, not cowardice. Unless you were a total nihilistic sadomasochist who didn't give a damn about yourself, you would feel fear when someone with many times your strength closes the distance on you in combat, and you wouldn't just let them whack you because otherwise it would be a quick and stupid death.
Moreover, he doesn't display any whining or mercy-pleading when he's down, and literally dies smiling.
I saw your edit descriptions on MCU Mysterio's page and you sounded so entitled lol. Your logic sounds like anyone feeling fear when approached by a guy who survived a direct hit from a train is a coward. No, all people who aren't completely deranged will feel fear for their lives; cowards let that fear control them. Mysterio isn't that, he's just a person smart enough not to just let themselves get whacked by a person strong enough to kill them in one punch.
Not to mention that he has the EDITH glasses that allows him to control the drones. If he gets punched in the face with those glasses on, it's game over; he would have no control over his means of conducting his operation, because either the interface would be destroyed or Spider-Man would take it. Either way, it would have eliminated all chances of possible counterplay. So a person in Mysterio's situation would be utterly stupid to stand there and take a superhuman punch.