Talakeal I'm going to say:
First, Decide on how you want to run the games; consider adding the "Absent Rules" by OldTrees1 in Post #363. As well as any other advice you feel applies.

Inform everyone in the Game of what the Style and Rules are, and stick to them.
Adjust things as you feel needed.

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Without going back and reading everything posted, it seemed that you were stuck with:

1) keeping Legendary Actions, and simply tolerating complaints.

2) exchanging LA for more Monsters.
Even if considered part of the BBEG.

3) completely removing LAs, and letting the PCs p'wn your Boss Monsters.

But, that even doing each of those things, did not solve the problem the players had with the Game?

Am I close?
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Without knowing a lot more about the other Players, I feel that I can't give any suggestions.
Maybe assign each a Codename - like you did with "Bob" - and specific information on what their Style is (or main complaint about the game)?

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Seriously, Bob should not be playing any RPGs; not even Video Games, and especially not tRPGs.
Play battle games: Napoleon-based armies like Warhammer 40k, or guerilla-type games: like Star Wars "Armada" or "Car Wars".

Just don't be surprised when Bob gets upset when he loses.

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I still advocate my suggestion from Post #357.
Talk to the Group, and if they want to keep playing, find a place away from Bob.

If you do keep Bob, let him Storm out of the room - ignore anything that has a negative effect on the other PCs.

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Hope this helps.