I would have Finn Balor be the one to retire him. I've been saying this for a while but I've been wanting "The Deadman vs The Demon King" for as long as I have known about Undertaker and Balor. Yes, Taker wouldn't be able to keep up with Balor (age ofc) but it could still make for an entertaining match.
If Balor's injury wasn't as significant as it was then I'd have him return at the Rumble. I'd take Enzo out of the 27 spot, and move Goldberg/Taker/Roman down one spot. This would leave the #30 spot for Finn Balor. I'd have him come out, do his normal thing with the paint while the crowd/announcers go nuts. Enter Finn into the rumble, with the rest of the competitors being the same except for Enzo. I'd have Goldberg and Brock do stuff for like a minute or so, with Reigns eliminating Brock with help from Goldberg, who would eventually eliminate Reigns (This can set up the goldberg/owens match at fastlane to be a triple threat. I'd have the match be similar to what it was but with Braun costing Roman, and them having a match at 'Mania.) Roman eliminating Brock can ultimately set up their feud, which seems like will happen soon.
Back to Balor/Taker. The two of them would have a staredown similar to what Reigns/Taker did and I'd have Balor eliminate Undertaker nearly the same as how Roman did it. He'd use some heelish tactics, which I will explain. On RAW he'd do his return stuff but Taker would come out and talk about Balor eliminating him and how no one crosses the deadman like that without punishment. He challenges Balor to a match, at Wrestlemania. The Demon vs. The Deadman. I wouldn't have Finn put in a match at Fastlane because I want to focus on the Taker/Balor storyline. Something could be done, perhaps a segment with the two at the PPV though.
Going to the weeks before Wrestlemania we see Finn grow restless and distraught, and unfocused because Taker has been getting in his head. During all of this, we see Finn walk by or talk a little to Gallows/Anderson in the locker room. We'd have a tag team match like the recent one where Finn and two others faced the Club and Joe perhaps, with oc the babyfaces going over. But Finn wouldn't fight Gallows/Anderson, for whatever particular reason. Back to Taker, Balor notices whenever he has the segments involving the subject of Taker that the crowd is conflicted but is leaning towards Undertaker.
The last RAW before 'Mania I'd have Undertaker appear and have a segment with Balor (this would be his first live appearence since Fastlane/Rumble) and tombstone Finn. Undertaker would be walking back to his music to only see Finn sit-up like Taker is known for, just staring him down.
At 'Mania, it would be The Deadman vs the Demon King. "Battle of the Underworld", I don't really know lol. It would be epic, though.
Balor would carry Undertaker throughout the match until Taker gets the upper hand near the end. However, I'd like to have the same/similar ending happen where Finn out-wrestles Taker due to him getting exhausted (making Taker feel human). He'd run around him, hitting him like Roman did. A few Coup De Grace and Finn would get the win. When the match ends, Undertaker just lies there like the Taker/Roman match with Finn just standing up and staring him down. Then we'd hear The Club's theme roar throughout the stadium while the crowd goes crazy. Gallows/Anderson would appear with facepaint (I think they wore facepaint when they were in the Bullet Club, idk really. This would make them menacing though after their title loss.) and Balor wouldn't move a muscle. He just stares at Taker while Gallows/Anderson run down to the ring. Without hesitation they attack Taker with the crowd booing their minds out, but Balor doesn't do anything. After a minute or so he grabs Gallows and tells him and Anderson to knock it off. They fake leaving the ring until Balor runs past them and brutally attacks Taker. Gallows and Anderson just watch laughing, as Finn hits one final..devesating..Coup de Grace. They all leave with Finn's music playing. Finn Balor Heel turn. Balor Club stable created.
I'd have the same events happen with Taker (how he got up and left at Mania this year).
This would give The Club some relevance, seeing as they really..really need it. They then can go into a feud with the Hardys, while having Balor's back.
Finn would explain why he did what he did, and why he let happen what had happened. He says it's time for change, and a new era has begun. The Era, of Balor.
Having Finn be heel can do wonders, if done right. This would be the perfect way for him to get heat, especially Gallows/Anderson as well. This would give them relevance, which they rightfully deserve.
This can set up a Shield vs Balor Club match (in the future), Aj Styles vs Finn Balor inter-brand stuff (SD vs RAW basically), etc. This may sound sloppy a lil bit but that's because I wrote this all at once, lol.
