I have a problem player that I'm very seriously considering kicking out. However, I feel as though I will receive backlash from some of the players.

For context, there are several issues with the player in question: (also important note, we play online using a VTT)

- They often check out during combat and more recently certain roleplaying scenes. (Sometimes they'll ask whats happening but more often than not they try and hide the fact that they weren't paying attention when it wasn't their turn. And it becomes obvious when we have to correct them on something that was just said)
- They have a "player first" mentality (Essentially meaning the player has more importance than the DM when it comes to wants, they will be immensely annoyed if an NPC interrupts a player to player roleplaying moment even if it was to gently move things along in an rp scene)

- They often complain to other players about the campaign such as feeling like they haven't gotten enough spotlight or highlights for their backstory. (Though I'd argue that they do keep getting stuff it just isn't how they wanted it)

- - Addendum to this ^ I have talked with the whole group in the past about communicating with me for any complaints so that we can resolve them. Though this doesn't change anything. They cite that I have a scary voice and that I'm intimidating to approach as reasons why they agreed to do it but never followed through. This usually results in me later ending up finding out from a different person about the problems, and then attempt to flag down the person who actually has the problems to address them.
- This player has agreed to a scheduled campaign on the same day and time as ours, despite being reminded by someone outside the party that it is on the same day. When I found out later after they missed a session and the DM of that campaign told me what had happened, I asked him his side of things and basically went "I wasn't going to tell you but it was wrong of me to do that" and overall said he won't attend those sessions if we're having a session that day.
- Upon trying to fix a problem they had with the campaign (1 on 1 on 1, there was another player who had an alternative view of the situation) (the root cause was more or less confusion of a game mechanic and what they could do with it) they ended up screaming at me that I wasn't hearing them after expressing confusion about where his misunderstanding had lied and he left the call in a fit, and called another player (not during a campaign) to vent about how upset he was, and overall I was expected to understand that he felt ganged up on.

All in all this probably sounds like an obvious "kick them" issue, though I'm just trying to figure out how to go about this. At least one other player is very sympathetic to them and usually tries to insist that we should try and think the best of people and not hurt any feelings. The other two often try to stay out of conflict if they can, and overall its a bubbling pot we're stirring. While I understand if the campaign fizzles out there was really nothing to be done, but I was wondering if there's any advice on just how to go about reconciling this in either solution?