You should never go full retard...

** Targeting systems **
Amarr - Radar
Caldari - Gravimetric
Gallente - Magnetometric
Minmatar - Ladar

** Damage types **
Guristas - Kinetic / Thermal
Serpentis - Thermal / Kinetic
Blood Raider - Thermal / EM
Sansha's Nation - EM / Thermal
Angel Cartel - Kinetic / Explosive / Thermal
Minmatar Fleet - Thermal / Explosive
Amarr Navy - EM / Thermal

** Best Damage to NPCs **
Guristas - Kinetic
Serpentis - Thermal
Mordus - Thermal & Kinetic
Blood - EM & Thermal
Sansha - Thermal
Angel - Explosive
Mercenary - Thermal

** Stacking penalties **
1st mod = 100.0%
2nd mod = 86.9%
3rd mod = 57.1%
4th mod = 28.3%
5th mod = 10.6%

Amarr, EM / Thermal EM (47%) / Thermal (42%)
Caldari, Kinetic / Thermal Kinetic (51%) / Thermal (48%)
Gallente, Kinetic / Thermal Kinetic (60%) / Thermal (39%)
Minmatar, Explosive / Kinetic Explosive (50%) / Kinetic (31%)