Damage to tank:
Guristas - Kinetic / Thermal
Serpentis - Thermal / Kinetic
Mordu's Legion - Thermal / Kinetic / EM
Blood Raider - Thermal / EM
Sansha's Nation - EM / Thermal
Angel Cartel - Explosive / Kinetic / Thermal
Mercenary - ALL
Rogue Drones - ALL
Amarr Navy - EM / Thermal
Caldari State - Kinetic / Thermal
Gallente Navy - Thermal / Kinetic
Minmatar Fleet - ALL (varies)

Best damage to deal against NPCs
Guristas - Kinetic
Serpentis - Kineti
Mordu's Legion - Thermal / Kinetic
Blood Raider - EM
Sansha's Nation - EM
Angel Cartel - Explosive
Mercenary - Thermal
Rogue Drones - EM
Amarr Navy - Thermal
Caldari State - Kinetic
Gallente Navy - Thermal
Minmatar Fleet (thukkers) - Thermal