Just because of that Katchaaaau! Mcqueen has always been an iconic character in Disney Pixar Studio, In my opinion, he should be a damage character similar to Dash, due to the speed and has inspiration skills.
Ok Let´s try some skills:
White Skill: Hudson Hornet´s Mud Drift: Mcqueen Runs into mid of the enemies, doing 3 drifts, hitting all enemies around him causing all enemies hit by xxxx damages each time and reduces their movement speed by xxx%
Green Skill: Victory Lap: At the beginning of combat, Lightning Mcqueen Runs through whole screen with full speed, causing them xxxx damage (similar with quorras)
Blue Skill: Kachaw: once in a while Mcqueen flashes his lights blinding all enemies for 5 seconds, increasing their missing chance on all attacks by 70%
Purple Skill: Speed, I am Speed: Victory Lap now also increases all allies attacking speed by 30% for 7 seconds
His basic stats should be: High Normal Damage, High Skill, Average HP, Average Defense and Low Reality
Hope you can make some awesome suggestions!