The worst.

[Denelo]

Mmkay, I'll play. You forgot bombers in your list, FYI.

Worst Light Fighter: Griffin (OLOL Eagle-sized LF)
Worst Heavy Fighter: Falcon (OLOL Eagle-sized HF with LF-ish guns)
Worst Very Heavy fighter: Virage (... Just terrible)
Worst Bomber: Broadsword (Big, slow, and... light bomber armor and core?)
Worst Freighter: CSV (100% pure abject fail)
Worst Transport: Assuming it counts, Prison Liner (3300 cargo, used to haul prisoners - possibly the least-profitable cargo around - and... almost no one can use it? Also, talk about battlecruiser-sized/speed transports). If not, Firefly (due to the terrible turret arcs and low hold size).
Worst Gunboat: Bretonia Gunboat (seriously, it's the size of a cruiser... literally. It has a bigger forward profile than most cruisers, and doesn't have anything to make up for it but a little bit of extra armor)
Worst Cruiser: Umbrage (formerly the Corsair Huntress, and based on long-standing dev policy on imports, I seriously doubt the arcs have changed. Blind spot? What blind spot?)
Worst Battlecruiser: Argus. Don't even have to explain this one.
Worst Battleship: Liberty Carrier (Lemme see... Twice the size of an RM BS? Check. Horrid textures? Check. The same forward firepower as an Osiris, and almost half the rear firepower? Check. Anything at all to make up for these things? Not really.)