Anime: Bruno appeared in To Master the Onixpected!, but it's possible that Bruno appeared already in Pokémon - I Choose You! as the shadowy Trainer using Nidorino and Onix. His English voice actress is Maddie Blaustein and his Japanese voice actor is Toshiyuki Morikawa.

While Ash was preparing for the Pokémon League in Kanto, he found out that Bruno was training in the mountains near Pallet Town. Brock was enthusiastic about meeting Bruno, so they took Misty and headed towards the mountains. In the local mountains, it was known that Onix grew much larger than usual.

After Bruno saved them from one of the giant Onix, Ash and Brock begged for Bruno to take them on as students. Bruno agreed, as long as Ash and Brock would do anything he said. Bruno had them chop wood, carry water, and carve chopsticks - amongst other chores. Misty began to suspect that Bruno was a phony.

Brock decided to prove how amazing Bruno was by surprising him with a sneak attack. He assumed that Bruno's reflexes would be so amazing, he'd stop Brock with ease. Brock nearly ended up knocking Bruno unconscious. Bruno admitted that he didn't know any secret techniques on how to train Pokémon and just wanted to have someone to do chores for him.

Later, the kids were again chased by a giant Onix. Bruno calmed the giant Pokémon, and it decided to join Bruno's team. Bruno then said that the only true secret behind Pokémon training is that Trainers and their Pokémon should care for each other.

Bruno has amazing physical power and agility in the anime, and appears capable of using them with almost superhuman expertise.

(Source: Bulbapedia)