Yeah Ugly also has a second form but given Murata often buffs the characters compared to webco I didn’t include him here. I dont really remember how much powerful Ugly second form was
Base form vs Ugly I don’t know. Ugly is super powerful but Kabuto even if crazy is quite smart too.
And Base Kabuto destroys early Genos like nothing. And I don’t know if that Genos is far below TTM.
About Carnage mode we know that Darkshine can beat Carnage mode but after a very hard 15 minutes fight. I don’t know if Darkshine needs 15 minutes to erase Ugly. Darkshine took hits from half Monster Garou without being really hurt.
His Second Form made him much Bigger but he only defeated Genos, after that Bang came & One-Shot him, so yeah can't say much about it, will have to wait until Murata draws it & Buffs him
Fuhrer Ugly definitely hits so hard but he didn't show any intellect or speed or that he can tank powerful attacks. Kabuto on the other hand is extremely Fast, smart & have Insect Senses (+Flight), he is also very tanky & both Dr. Genus & Darkshine said that Insect Strength is the Best.
Also when we compare their Fights:
Base Kabuto One-Shot Genos even after G4 Upgrade (Where he was Strong enough to Defeat almost all Demons)
He can stop & redirect a Big Fire Blast from Genos with just his Breath (To the point, Saitama got hyped & thought He can challenge him)
He lasted 15 Minutes against Darkshine & the latter really praised him, even though Darkshine can handle Garou quickly (Before Transf)
He also defeated Base Metal Bat quickly even though Base Metal Bat is still strong enough to One-Shot some Demon Level Monsters
Also Genus believed no one can stop him even though he studied half S-Class Heroes
Not to mention that Bug God seems like Top 3 Demon Level Monsters & Kabuto is like Dragon Version of that, so more praise
On the other hand, we have Fuhrer Ugly:
He failed to catch or defeat Sweet Mask even though he was powerless to do anything
He wrecked TTM but that is not very impressive
Even Half-Asleep Garou did the same with PPP & even after he woke up he couldn't last long against Darkshine
He also showed lack of speed & relies on dirty play to defeat his Opponents
I simply believe Genus created better Monster