This is hard due to differing play styles, but this is my opinion. I will come back to some later.
Best Anti-Infantry for Vehicles: Lightning with L100 Python Heat and Thermal Optics. Proximity Radar, Fire Suppression and Racer Chassis. The Viper and HE are better against infantry, but are ineffective against tanks. The AP has no splash damage at all. The Heat has good splash damage and is effective against vehicles so is the way to go.
Best Anti-Infantry for Infantry: Max with twin shotguns or Heavy Assault
Best Anti-Infantry for Aircraft:
Best Anti-Vehicle for Vehicles: Vanguard with Titan-150 AP (max zoom) and Halberd or Enforcer Vanguard Shield, Auto Repair and Rival Chassis (changed my mind to Racer Chassis)
Best Anti-Vehicle for Infantry: Max with twin AV, Heavy with AV (lock on) or Engineer with Mines and AV Turret
Best Anti-Vehicle for Aircraft:
Best Anti-Aircraft for Vehicles: Lightning with Skyguard (max zoom) Fir Suppression, Auto Repair (or Top Armor) and Racer Chassis
Best Anti-Aircraft for Infantry: Max with twin AA, Heavy with Annihilator(AA and AV lock on)