(It's not "The Relatable Iron-Man" or "The Balanced Iron-Man" or
"The You're-Better-Off-Playing-A-Mutant Iron-Man"...
it's THE INVINCIBLE IRON-MAN)
Strangely enough, all of these guidelines come from an old anime.
So, let's take lessons... from MAZINGER Z:
As opposed to contemporary shounen anime, Mazinger didn't intend to sell you the "Dragonball Z formula" where a weakling is constantly picking fights with someone stronger than him until he eventually surpasses and beats the villain (sorry to burst your bubble but, if every single enemy is always stronger than the hero, is he really a badass? No, he isn't). Mazinger was originally the giant robot to end all giant robots, and indeed he was famous for making short work of rival robots in a straight, fair fight.
The father of the "Super Robot" genre
So, how did Go Nagai keep Mazinger's fights interesting? Here's how:
Rather than resorting to Dragonbullshit or Green Rocks Of Lazy Writing, what Nagai did was handicapping via unusual circumstances that often kept Mazinger out of his element: Flying enemies, submarine enemies, illusionists, and otherwise enemies with "battlefield control" abilities. I'm not sure how much of this was Nagai and how much his editor but, in addition to this, whenever the enemy became repetitive with the same gimmick, Mazinger got an upgrade in order to turn the circumstance a non issue in the future (he got adapted for aquatic combat after the first 2 submarine enemies in a row, and after the first 3 flying enemies, he got his aerial upgrade) and thus avoid the Green Rocks Of Lazy Writing.
To keep things fresh, sometimes instead of handicapping circumstances, the enemies would force the hero to change tactics by being immune to whatever quality was becoming a comfort zone: Sometimes they'd be immune to whatever weapon he had been more consistently relying on, and sometimes enemies would have the specific ability of nullify his super-alloy (forcing him to dodge and use strategy rather than just tanking every enemy attack).
Then, there was always the occasional "puzzle monster," which could only take damage under specific circumstances (example: Twin mechanical beasts that regenerated all damage unless both were destroyed at the same time), or that required a specific attack sequence, or that were only vulnerable to a specific weapon at the right time (example: A photon beam right at the moment he monster opens his chest cavity to unleash its biggest weapon).
In none of the aforementioned cases the mechanical beast was innately stronger than Mazinger, it was the handicap that leveled the field. Only in a couple cases (one of which was the series' end) Nagai resorted to the "strictly dramatic" encounter where the enemy/circumstances were insurmountable and the only reason the hero lived to see another day was by some contrived serendipity that opened a window of opportunity at the eleventh hour... and that was indeed good since narratively these are the most boring: The author got the hero into an impossible situation only to get his bacon out of the fire himself, thus there was zero meaningful input from the hero (needless to say, this is even more boring in a tabletop game, since it's interactive entertainment and the players' choices are supposed to matter).
Those are my two cents, take 'em or leave 'em. If any of this sounds like too much work for you, stick to low-powered games (plenty of them in the market, after all!).
