If you are referring to anti-trust laws preventing this, then MS would need to be buying a huge number of companies to monopolize the gaming market, not just Activision, in order to be in violation of this law.
They can "ask" gaming companies to use Azure if they want to run on Windows or Xbox. They can ignore Mac and PlayStation as platforms. They can bundle software licenses, payment gateways, and design hardware that only works in one ecosystem.
This is the modern monopoly. Good luck competing with it or avoiding their platform fees as you try to grow your revenue. You'll undoubtably wind up feeding your direct competition somehow or another.
> They can wield this power to force deals and push out competitors across their multiple business units.
The only way this would matter is if you can prove that they have some monopoly in any one market and use that monopoly position to drive up prices.
So if somehow could leverage their Windows OS as to sell games for 1000$ rather then 100$.
Microsoft does not have monopoly in any one market as far as I can tell.