After completing the Indigo League and Orange Islands in the Kanto Region, Ash and his friends moved onto the Johto Region and the second generation of Pokemon. Ash kept several of his Pokemon from Kanto with him as he explored Johto, but he also caught many new species native to the region that went on to battle at his side.
Ash caught fewer Pokemon here than he did in Kanto. This also means that almost each of his Pokemon caught in Johto was intended for battle and stuck with him throughout the region. Today, we are going to rank Ash's Johto catches from least powerful to most.
8 Beedrill
Ash briefly had a Beedrill when he participated in the Goldenrod Bug Pokemon Catching Contest. Capturing the Beedrill won Ash the contest, though he didn't keep it for very long after the fact. He gave the Beedrill to fellow trainer Casey, as it matched her aesthetic theme.
7 Larvitar
Larvitar hatched from an egg given to Ash by Professor Elm. It never battled for Ash, as it was already scarred from the ancestral memories of poachers attacking its Tyranitar mother. Eventually, Ash was able to find Larvitar's mother and return him to her. Ash and his friends also helped fight off the poachers that were still harassing Tyranitar.
6 Donphan
Ash received Donphan as an egg that hatched into a Phanpy. Despite its bravado, it lost several battles in a row--even ones where it had the advantage as a Ground-Type Pokemon. However, it came back to redeem itself when Ash went off to challenge the Battle Frontier. It protected Pikachu from an Elekid and later evolved into Donphan to bring down a Team Rocket robot.
5 Totodile
Totodile came into Ash's team after a battle between Ash and Misty. Totodile is a Water-Type Pokemon and would have been a natural fit for Misty given that she is a Water-Type Gym Leader in Kanto. However, Ash won the contest and got to keep the Totodile. It was a fun-loving Pokemon that often danced and played pranks on other Pokemon.
It still fought well for Ash and became a vital part of his lineup. It took down a Kingdra in the water-based Whirl Cup, and it even brought down a Charizard. It lost a fight to a powerful Sneasal that was then caught by fellow Pokemon Trainer Harrison. However, Totodile got its revenge when Ash battled Harrison, and Totodile took Sneasal down.
4 Noctowl
Ash caught Noctowl already fully-evolved, and it's a Shiny Noctowl on top of that. It fought on Ash's behalf throughout his Johto journey. Despite being a Flying and Normal-Type Pokemon, Noctowl is known for its Psychic-Type attacks and often used them in Ash's service. Noctowl used Hypnosis to best a Fearow by tricking it into believing Noctowl was a Charizard, he took down Gym Leader Morty's Gengar, and it even kept a plane from crashing in Olivine City.
3 Heracross
Heracross is a Bug and Fighting-Type Pokemon, and it was the first Pokemon caught upon arriving in Johto. It has a sweet tooth that prefers tree sap, and it's also one of Ash's most powerful Pokemon caught in the region. It took on the likes of Donphan, Scizor, and a Magmar while Ash traveled through Johto, and it even took down a Venusaur later in the Hoenn region.
2 Quilava
Ash caught Quilava as a nervous and slow Cyndaquil on his way to Azalea Town in Johto. It's a Fire-Type Pokemon that inevitably proved helpful during Ash's showdown with the Bug-Type Gym Leader, Bugsy. It took on Bugsy's Scyther, Bugsy's most powerful Pokemon, and won the duel. It later learned the art of speed in a battle against a Skarmory, and it later took down Jasmine's Steelix and Pryce's Dewgong, both of whom are Gym Leaders in the region.
Cyndaquil wouldn't evolve into Quilava until Ash traveled to the Hoenn Region. Cyndaquil joined the battle against Team Rocket but evolved into Quilava when it found its attacks weren't strong enough. As Quilava, it took Team Rocket down with ease and sent them blasting off again.
1 Bayleef
Bayleef was arguable Ash's greatest asset throughout the Johto Region. Ash caught it as a Chikorita, and it stubbornly battled against Ash's Charizard. Once Ash caught Chikorita, she immediately grew intensely attached to Ash. It even fought off other of Ash's companions to maintain Ash's attention. Chikorita won out against Bugsy's Spinarak despite the type disadvantage, and it beat Misty's Staryu when Ash fought Misty over Totodile. She later took out Jessie's Arbok with a single Tackle, and it evolved into Bayleef to stop another Team Rocket robot. It also single-handedly took out Chuck's entire team after the Gym Leader's Poliwrath made short work of Pikachu.