The Red variant of Master A. has high health, very high DPS, quite long range, and the ability to slow cat units. Not too much of a threat by itself, it can become deadly when backed by powerful friends, such as the Gory Blacks and Angelic Gories in Pecking Order.
Professor A.'s biggest weakness is units that outrange it. Li'l Nyandam and the area damage from Crimson Mina and Prisoner Cat are all great no-gacha ways to get rid of it. If Professor A. has support, try and bring it down first — it's far, far easier to kill an unprotected Professor A. than one with endless waves of tough enemies to fight for it. Awakened Bahamut may also get a hit on Professor A. if you get incredibly lucky with timing.
Even though he's still a college undergrad, his research into dirty stuff is so in-depth and thorough that his friends call him Professor. Dating experience is still somehow zero.