Shouto originally had a cold and aloof personality due to his abusive upbringing under his father Endeavor. He was single mindedly focused on rejecting his fire powers to spite his father.
After his fight with Midoriya and reconciling with his mother, he began to ignore his hate of Endeavor and began to use his left side in battle. Along with this Shouto began to upon to the people around him and became a more warm and sociable person.
Inspite of how he comes off Shouto is s hero at heart and prioritises rescue and will only use as much force as necessary in a fight.
Shouto's Quirk is known as Half Cold Half Hot and is a perfect fusion of his father's pyrokinesis and his mother's cryokinesis. From his right side he can drastically lower temperature and create large amounts of ice that he can form into crude shapes to increase his mobility, defend himself or support allies. From his left he can drastically increase temperature and generate large amounts of flame that he can focus into a point to increase his attack power and speed. If he overuses either side he will suffer frostbite (from his ice) or heatstroke (from his fire) however both drawbacks can be mitigated with the opposite side.
By cooling the surrounding air and rapidly heating it he can cause the air to rapidly expand to create blasts of varying power.