Even though the training was tough, he persevered and finally won the competition.

persevered 是动词 persevere 的过去式，persevere 由前缀 per-（表示"完全、彻底"）和词根 severe（"严格、严厉"）组成，意思是"坚持不懈、持之以恒"，指在面对困难时仍然持续努力不放弃。