I have a question how come Imam Ali had wounds after battles if he was so good at fighting. Shouldn't he have come from the battlefield clean like the event where an arrow pierced his foot. If he was so strong and brave then why couldn't bear the pain of the arrow being pulled out of his foot

It’s not possible to him not to have wounds. The enemies had weapons too. Even the holy prophet had wounds during the battled of uhud, his journey to Taif etc
Having wounds do not decrease their values or merits