Gonna have to disappoint you there - I am
shit at remembering names. To make it worse, IIRC it was being translated by Asmodeus Scans, so the existing chapters got nuked off the site when that group got banned.
But the basic premise was "Man isekais into overweight villain dude, gets in shape, absolutely masters fire magic, starts saving all of the heroines because he's OP as fuck."
That one reduced the training arc to a single chapter and jumped straight to the "OP as fuck" action. Last thing I can remember about it was some two-page spread with the MC manifesting a giant fire salamander thing (like Ifrit from this work, but actually dragon sized) to fight some giant monster.
Now that I think about it, it was basically someone taking L99 Villainess and turning it into harem slop I guess?