There was this one time I came across a Mega in For Glory. He wasn't bad. He was definitely less experienced at competitive Smash than me.
He started the match with reckless Fair and Bair approaches but wasn't terribly stupid with them. It took me until I started punishing his landings with USmash OOS to get him to stop. Instead he'd wait instead of bair on landing and punish me with a grab if I Usmashed OoS.
He kept a general aggressive air strategy, but slowly calmed down after he'd lose repeatedly to my more patient, projectile-based playstyle. He eventually started to win matches against me as he adapted to me and the fights got pretty heated. I sill won a majority of them though but he definitely forced me to adapt and think more about my strategy.
We'd even invoke gentlemen's rule and SD after the other SD'd on first stock. At some point, I was getting him with a lot of deep edgeguards (which is where I clearly shined in 3 hours of playing him. That and deep recoveries.)
So at one point I ran off the stage and started doing walljump aerials to show him a way of edgeguarding and he just kinda stood there watching, and started practicing them himself.
He tried to use them in later matches so that was neat to see.
Eventually the lag got so bad so he left, but it was a fun 3 hours.
In terms of people getting salty over my Mega. They tend to go Mario/Villager/Fox in order to counter what they feel is projectile spam.
Little do they know, I actually know how to play a minimalist projectile game with Mega lel.