Finally, let's all debate and comment on this wonderful game! And first I'd like to say: you're fucking stupid, you sons of bitches!
Kidding, kidding
I remember writing a big ass paragraph a while ago summarising all the ways Deryl is just straight up being clowned on for most of the game and how he just can't ever seem to win. From his perspective, no matter how much he stacks the deck in his favour, no matter how much monster knowledge he has, no matter how much custom built clones he creates to exploit weaknesses or proxies he has to try risky strategies he still gets his ass beat. Almost every fight this man has ever been in has involved Apostle/Greater spawns - A.K.A some of the most busted people in the entire verse. He just can't catch a break.
Second generation spawn like Alice and Shen, operating in the low tier levels of comic book character intelligence, ruthless combat pragmatism, chaining power combos together like its fucking Devil May Cry with all his monster-based equipment and he still gets folded like an omelette due to being a glass cannon. Part of the reason why I enjoyed the Cole VS MC and Deryl fight so much is that I finally got to see the two of them work immaculately together, and Deryl finally worked out how to take a hit.
You're right, and to be quite honest, Deryl is the kind of character that if he were the protagonist, the whole game would be broken. Deryl is intelligent and his power could well be considered one of the top 10 or 5 most powerful in the entire game. He's able to recreate everything he understands, whether it's organic or inorganic, which makes him one of the weakest in the game, because he needs to know his opponent, create a strategy, in order to have a chance, he's not someone made for hand-to-hand combat, as you said yourself, and as you also said at the end, it was incredible to see him fighting alongside Mc against Cole.
Yeah I still call bull on the MC evolving during the Rebis fight. Though it does pose an interesting question. How strong would have Deryl been if he was able to defeat MC and complete his plan of becoming a Rebis.
Powerful, but above all, dangerous, because it could always become stronger and stronger, always be reborn and become more powerful, limit? I can't say, maybe he could become as strong as level 5? Difficult, but I don't doubt it
To be fair the twins abduction was far more a HERO's failure than anything related to Deryl, like Mc tells him in one of the choices from last update, they didn't have any chance against Devana and Evander as long as Shen was also there.
Now being beaten in a single attack was eye oppening for him and lead to creating the Mecha and all, and when fighting a lvl 4 Cole we learned that this thing can take a beating, Devana's bombs were enough to knock down Deryl but not Mc so i doubt something like that would work on Deryl again, she also doesn't seem very keen on creative use of abilities and relies on Tanos for "blueprints", her power might be "better" but i doubt Deryl will take long to surpass her.
It was the revelation, basically, that even as a level 3, he can't allow himself to be "exposed"