I've seen several people post that they gave up on fighting the Dark Lord. I almost gave up too, partly because I loathe bosses with health regen. It's my kryptonite. I was stuck in an endless loop where neither of us would die, and I was about to call it quits. After spending about 20 minutes on just the first two stages (out of 5), I changed up my strategy and beat him in 15 minutes. I'm a decent player but far from master or elite, so I hope this helps anyone who gave up on a tedious and repetitive final boss.
DISCLAIMER: I have no pride about it, I lowered my difficulty from UV to the lowest level. HOWEVER -- I don't think it did anything. I literally don't think it makes a difference. I already wasn't dying, and he'd regain the same amounts of health, so it didn't seem to make a difference. The health regen is what makes this battle so difficult aka time consuming, otherwise it's pretty standard stuff.
1) Most importantly, I decided to stick with ONE weapon: the chaingun. Unlike the Marauder, the Dark Lord can be hit with any weapon when he flashes green. Just a single bullet from the chaingun is enough to stagger him. As soon as that happens, hammer time him (really not an option but a necessity) and then turret gun him. After 2-3 times he'll go down in each round. Maybe 3-4 times in the final round. I stopped worrying about switching weapons like I do in the regular game and it freed me up to focus purely on the arena. I highly recommend this if you're stuck or annoyed. The chaingun is more than enough to do everything you need.
(BFG blasts meanwhile are basically meaningless for this battle.)
2) Always shoot the dogs. It's the easiest way to charge the hammer. The basic combat flow should be hit him when he's green, chaingun him, then back off, shoot the dogs, get the hammer back and rinse and repeat. Chainsaw fodder along the way to keep ammo up. That's the basic combat loop. It's all very predictable.
3) Be aggressive. The game is pretty vague, but basically go after him so you're almmmooosstttt in sword range. This greatly increases your odds of getting the green flashes. Hanging back will prolong the fight way too long. He flashes green way more if you're going directly at him but backing off at the last second.
4) In the later stages, his shield attack is the most annoying thing ever. You can get stuck on the phantom monsters in the arena, and even when dash dodging it's easy to get hit by him and he health regens a ton with each hit. What helped was circle strafing around the outer rim of the battlefield. Especially after you strike him, and you know the dog attacks and shield attacks are coming, just go in a circle along the outer edges. This makes it easier to keep an eye on him so you can dash strafe away from his attacks. It also keeps the phantom monsters always a little behind you so you're less likely to get stuck on them and then hit by the shield attack. Once you've done this, go back to being aggressive so you can get the green flash again. Rinse/repeat.
And that's it!
Like I said, I *LOATHE* health regen on bosses, and I didn't actually think I'd finish this fight. I planned to just watch it on YouTube. But after figuring this out, it became way less tedious and I pretty much powered through it quickly with little frustration. I still think it's a terrible, lazy, tedious final boss, but this at least helped me get through it so I could complete TAG2.
