Guardian is an expansion supercar, and requires the starter kit to function properly.
Guardian is a fast supercar, capable of outrunning any other car, save Groundshock, Ice Charger, and Thermo. She uses her high speed to compensate for lack of defense, but has a high special item capability and specializes in weaponry that hacks other supercars - damaging their steering, negating their armor, or forcing them into entrapment fields. Guardian has held the top spot for special item functionality and capacity, although Groundshock comes close.
Guardian comes short in the firepower department. Guardian can only equip two weapons at a time, and the Sonic Blast and Scramble Mine cannot be upgraded past level one, limiting their effectiveness. Furthermore, Guardian's long range weapon needs a decent amount of trigger time on tougher targets like Big Bang and MXT, and as such the commander needs to plan their attack accordingly.