What gets good Ratios: (depending on tech lvls)
Fighters kill the following ships easily
1x Fighter : 1 fighter OR 1 bomber OR 1 Recycler
2 x Fighter: 1 heavy bomber OR 1 Corvette OR 1 outpost ship
4 x Fighter: 1 ion bomber OR 1 destroyer
7 x Fighters : 1 Frigate
Destroyers:
1 x Destroyer: 1 Ion bomber
2 x Destroyer: 1 Frigate or 1 Ion Frigate
5 x Destroyer: 1 Cruiser (just under half destroyers will survive)
12 x Destroyer: 1 Heavy cruiser (Roughly Half destroyers will survive)
Cruisers:
3 x Cruiser: 1 Heavy Cruiser (just under half cruisers survive)
10 x Cruiser: 1 Battleship (just under half Cruisers will survive)
58 x cruiser: 1 Dreadnaught (over half of cruisers will survive)
To take out, You should use
Fighters----------------------------------------Battleships or Fighters
Bombers---------------------------------------Battleships or Fighters
Heavy Bombers---------------------------------Dreads or Fighters
Ion Bombers-----------------------------------Fighters
All other unshielded units---------------------Fighters
Cruisers---------------------------------------Fighters or Cruiser/Fighter Mix
Heavy Cruisers------------------------------Cruisers AND Fighters
Carriers---------------------------------------Cruisers AND Fighters
Fleet Carrier---------------------------------Cruisers AND Fighters
Battleships------------------------------------Cruisers AND Fighters
Dreads----------------------------------------Cruisers AND Fighters
Titans-----------------------------------------Heavy Cruisers AND Fighters
Levis------------------------------------------Battleships and Fighters
Death Star-------------------------------------Battleships and Fighters
Barracks-Photon Turrets-----------------------Cruisers AND Fighters
Disruptor-Pring (including all shields)-------Heavy Cruisers and Fighters