If you want to hurt MS, assuming the ABK deal goes through in whichever form, you acquire publishers whose games are consumed by the mostly dudebro demographic that buys Xbox. That leads to the obvious conclusion, Western publisher acquisitions by Sony will hurt MS the most competitively-market share wise. If you notice, MS went after both Bethesda and ABK, publishers which serve their dudebro demographic best in anglo markets... and one of the many benefits is that it holds those games/ips in place instead of worrying about viability equations outside of MS's control with regards to those Games/IP's releasing on Xbox - coming as a result of market share erosion to Sony's Playstations platform OR if releasing on Xbox becomes expendable vis a vis exclusive agreements with Sony (which, Covid chip-shortages notwithstanding (beneficial to MS), should have been a significant issue for Xbox - more than what it's already).
With ABK and Bethesda out..... those in the U.S are EA, Take-Two, Epic Games, Warner Bros. Games.... while in Europe, Ubisoft, Embracer Group Holdings, CD Project Red.
Needless to say, all of the above are expensive as fuck. Only CD Project Red being on the low end due to the Cyberpunk debacle, and the smallest of the lot.
The only Japanese publisher that is currently healthy with mind-share in that Xbox dudebro demographic, although lesser to that of Western pubs is CAPCOM, NOT Square Enix. CAPCOM's IPs are still relevant to that consumer base, attract attention, generate sales, and thus its exclusion from that platform will cause market share erosion positive to Sony. The degree and numbers of those whose exodus are 100% corralated is always hard to say but we do know it happens, with the Xbox 360/PS3 generation being the best example of this.
So if you want to strategically send a big dick energy bang, and a safe bet bang too by buying a protected in-house (Japan) pub, you grab CAPCOM.
Square Enix, after selling its western oriented IP's provides almost zero value to Sony in its push to eat away at MS Xbox consumer base.
Square Enix is in no threat, nor will it be allowed to be acquired by a Western console manufacturer (MS), nor will Tencent or NetEase be allowed to gobble it up either (not past majority controlling shares anyway and without veto from Nintendo/Sony in the backroom). There is a reason Jap Pub giants haven't been 100% bought by foreign giants till this very day after several decades. It's politics, national, geopolitical business politics. Square Enix as is, in its current form is perfect where it's as it relates to Sony. To acquire them would be an unecessary expenditure, which should only be contemplated if Square is in serious hurt to potentially go under but as we've seen with Konami's fade to irrelevance, this isn't required either. As a rule, Japanese pubs are safe where they're given the current market environment. Thus Jap Pubs should not be priority targets, specially considering opportunity costs of acquiring someone in the Western market that has a greater chance of disrupting the competitive landscape - resources ($$) are always finite.
This fascination about "ohh Sony must buy Square Enix" is absolutely devoid of any reason or critical thought, and purely 100% emotional based. With that said, to throw a bone if you will, Square, by shedding the Western weight off, is a clean and easy acquisition that adds more manpower to the PlayStation Studios machine, while locking the future of Final Fantasy in Sony's hands (which is hard to say if it's a benefit or not to that franchise). Nintendo will have to be accommodated, but this was done many years before the split so I'm sure it can be worked out. The last thing Sony should do is endanger Nintendo's market position and share by excluding sources of content to Nintendo as Valve (of Steam, Steamdeck, Steam VR renown), aka MS's little loyal puppet, aka absolutely not Sony's friend but rival/competitor's accomplice in times of business war, is dancing around in the shadows of the handheld market. This is chess, not checkers.
Warner Bros. Games or CD Project Red should be targets. Warner's lot is down but DC IP's are an infinite wealth in the age of superhero's + MK = bliss under Sony's helm - it's all about the licensing contract length for the IPs. CD is self explanatory - world class world builders only requiring technical assistance/guidance and responsible supervision througout a project's lifecycle - leave everything else untouched.
EA/Take-Two/Ubisoft/Embracer are too expensive imo. EA/Take-Two would be industry shaking events - cause unlike MS, Sony actually manages projects, studio talent well, and is still the market share leader.
