a bomber.
well basically, alot of bombers can bring down anything.
but as a rule it probably goes down to something like
light fighter - LF/HF/VHF/SHF/B
fighter - LF/HF/VHF/SHF/B
super heavy fighter - VHF/SHF/B
Gunship - VHF(x3)/SHF/B
Gunboat - VHF(x3)/SHF/B
Light Cruiser - SHF(x2)/B(x2)
Cruiser - SHF(x3)/B(x3)
I wouldn't go further than this for now, but this is your average skills pilots. Ofcourse Cruisers or even Osiris ship class ships were taken down by two bombers but alot of it depends on skills and even more on skills of a person taking the shots.
You should probably look for yourself, or if you really require some training or something you could come to the faction thats really outside your player's ZOI and ask them for few duels.