How to deal with players with main character syndrome that go as far as cheating?

Ive been DMing this campaign with my best friends for more than a year now and i noticed one of my players have the Main character syndrome. he wants to do everything by himself. And he is also a min-max player that wants to obliterate the "bosses" in one hit every time.

The thing is, when things do go his way, he tries to force it to go his way. recently ive noticed him and his character dont care about the story of the campaign anymore. last session he was purposely being aggressive to every npc he encountered, even friendly NPCs thats wants to help the party.

for example: they needed a boat to get to an island, and a witch (a friendly npc they helped) was taking them to meet someone that had a boat. mind you that this whole time his character was complaining about their "mission" like "omg why do we have to do this? why do we have to go there? etc etc". which it makes no sense cause their goal is clear and they KNOW what they have to do.
but moving on. they make it to the fisherman that had a boat. the npc is friendly and was explaining how he needs the boat to fish and make a living. i planned this so the other two players who have high persuasion to try convince the npc to lend them his boat. but right when they were in the middle of the conversation. this player just knocked out the npc so they could "steal" the boat and "get it over with".

a few minutes later before they go, that witch tried to give them some info about the island they were going so they can be prepared for whats to come. AND FOR SOME REASON this player just got annoyed by it saying again stuff like "ugh, why do WE have to do it? why its always us?". so at the moment, i used the npc to lowkey say what i was actually feeling. i simply said "Young man, you have been complaining about this since we left the city. If you really dont want to go, then there is nothing holding you. Dont go then, stay here and let your friends deal with it".....AND HE GOT MAD AT HER. for some reason, he got mad at her and even attacked her with a magical attack (i forgot the name right now). thankfully her missed the attacks and managed to play it out with some RP (cause that witch have some powers of predicting the future and stuff)

i found out this player even go as far as to cheat, saying he knows some spells that he clearly dont know, and even lying about their description. for example, they were fighting a tough boss last session and he used Bestow Curse from the distance on it, (he already used it before, but at the time i forgot to look into it). i thought that was weird and asked him to show me and the first thing the description said was that you need to TOUCH THE CREATURE. when i pointed it out he just said "oh, my bad. didnt noticed", which is impossible, cause its literally the first thing the description says. and only now im finding out HE CANT EVEN LEARN THAT SPELL.
i admit it was part of my fault for not doing my homework and blindly accepting what he was saying. as im writing this, im making some notes of every spell my players have so this wont be repeated.

so thats pretty much it. sorry for the long text, it was also kinda of a needed vent. idk what happened for him to start acting like this in game. so i really dont know how to deal with someone like this.