Doom Reimagined - Doom 1 remade with Doom 2 enemies and weapons
That Nukem Guy amped up Knee Deep in the Dead (minus the secret level) by adding assets from Doom 2. It's nothing crazy but the difficulty really ramps up when you're expecting a few imps and cacodemons and you're met instead with revenants and pain elementals. Fortunately the SSG makes an appearance to level the playing field.
I've been playing more and more doom recently, and just having a blast discovering the WADs people have made over the years. It was such a formative game for me 30+ years ago.
Dunno if you're on !retrogaming@lemmy.world but looks like there's some love for doom over there as well