Going back to Doom Eternal for a bit, I think I could finally pinpoint why the Marauder (and by extension the final boss of the second DLC) is such a frustrating enemy. It's because fighting it is strictly reactive, whereas every other encounter is proactive. With any other enemy or grouping of enemies you dictate the terms of the encounter: what weapons to use, who to target, what to prioritize, how to maneuver and so on. Whereas with the Marauder literally the only tactic is to bait out an attack, and then counterattack. He decides when he's damaged, not you. While there are plenty of enemies with rock-paper-scissors type mechanics to deal with them (shoot the turret of the arachnotron, the guns off the Mancubus, grenades for Cacodemons etc.) they aren't the only way of dealing with those enemies, and you can ignore those mechanics altogether if you wish. With the Marauder I think the only way of damaging him outside of counterattacks is to make him block with his shield by shooting the BFG, and attacking him from the back while he's blocking. And even then I'm not sure if it works, I just saw that as a possibility.