Miles Morales has not always been part of the mainstream Marvel universe. The incursion destroyed the multiverse, and they eventually reunited as one world, with Miles Morales joining Peter Parker and giving the world two Spider-Man heroes. Before this, Miles was a young teenager trying to fight villains that were bigger and more experienced than him.
Those early battles are what formed the hero that Miles Morales would become. He fought men he had no chance of beating, but he willed himself to win. He defeated veteran heroes that doubted him and proved to a society that considered him a ripoff that Miles Morales' Spider-Man was someone no one should ever doubt.
Kangaroo
The first appearance of Miles Morales as Spider-Man was in Ultimate Fallout #4, which came after The Ultimates battled The Avengers and Spider-Man died saving Captain America's life. After this, Miles Morales decided he needed to fill in the role that Peter Parker left behind.
His first villain was Kangaroo, a former Ultimate Spider-Man villain. Miles beat him pretty easily, and it was a nice introduction for the new hero, although most people mocked him for wearing a Spider-Man Halloween costume. Kangaroo never fought another hero after this loss.
Electro
In the first four issues of Miles Moraes' single title, he never fought a supervillain, as he was just trying to discover himself. He finally got to fight someone in Ultimate Spider-Man #5. In that issue, Spider-Woman captured him and brought him in for S.H.I.E.L.D.
While talking to Nick Fury, Electro broke out of containment. This sent Spider-Man into action, and, when he slowed Electro down with his Venom Blast—a power Miles Morales has that Peter Parker didn't—it allowed Fury to shoot him dead. This battle served one purpose; it sold Fury on the idea of Miles being Spider-Man.
Omega Red
In Ultimate Spider-Man #7, Miles Morales was studying the original Spider-Man battling Doctor Octopus. He wanted to find a way to fight similar to the original, and, when he set out to practice, he ended up in a battle with Omega Red, who still wanted revenge for previous battles with Peter Parker's Spider-Man. This allowed Miles Morales to win a fight based purely on his skills. This was also the last time that Omega Red was ever seen again in the Ultimate Marvel Universe.
Ringer
In Ultimate Spider-Man #8, Miles Morales had to battle one of his most bizarre villains. He was out and dealing with his problems concerning meeting his Uncle Aaron and realizing he was the villain known as The Prowler. That is when The Ringer attacked the city.
This was another former Peter Parker villain and one that Miles Morales had to figure out a way to beat. This was also where he had to face his father for the first time after the fight. This marked the end of the road for this bad guy.
Scorpion
Miles Morales had to deal with his uncle, Aaron Davis, and in Ultimate Spider-Man #11, his uncle forced him to help him. Davis, The Prowler, offered to help Miles become a better hero and set out to have his nephew take on a real supervillain. This was Scorpion, who had taken over as a local crimelord.
Scorpion was also gunning for Prowler and Aaron sent his nephew after the villain. The two worked together and took down Scorpion. However, Miles wouldn't kill him and turned him over to the police, and he was never seen again. This is also where Miles became enemies with his uncle.
Prowler
In Ultimate Spider-Man #12, Miles Morales told The Prowler that he would never work with him again and would not be his enforcer. Aaron had staked his position as a new crimelord after Scorpion went to jail, and Miles decided it was time to stop his uncle.
This led to their battle, and it was against one of the most dangerous villains Miles Morales fought, The Prowler decided to kill his nephew, but one of his vibro-shock gauntlets malfunctioned, and Miles falsely believed he killed his uncle. This appeared to be the end of Prowler until the end of the Ultimate Universe, and it changed how Miles viewed those around him.
Batroc The Leaper
Everything changed for Miles Morales in Ultimate Spider-Man #13. That was the issue where he got an important phone call and went to meet Aunt May, Mary Jane Watson, and Gwen Stacy. However, before he could get there, he had to stop to battle a criminal Falcon and the Winter Soldier fans may recognize known as Batroc the Leaper.
Miles beat him, but he was a bit awkward in doing so, and Batroc never appeared again in the Ultimate Universe. However, the important thing about this battle was that Captain America witnessed it, and, between the death of Prowler and Miles struggling against Batroc, he told the young man he could never work as Spider-Man again.
R.H.I.N.O.
In Ultimate Spider-Man #14, Aunt May convinced Miles Morales to do what he felt was right no matter what Captain America told him. As a result, Miles went to help Cap in a battle that put a lot of innocent citizens and military officers at risk. It was against an armored warrior known as R.H.I.N.O.
The original Spider-Man had helped to defeat him in the past, and, this time around, Miles also found a way to stop him when Captain America couldn't. With this win, Miles won over Cap and earned the respect of the United States' most esteemed hero.
Hydra
In the storylines Divided We Fall and United We Stand, a terrorist organization known as Hydra used the Nimrod Invasion to ally itself with Thor and Hela's son, Modi Thorson. Together, they attempted to conquer the United States government through another American Civil War.
Captain America became the President of the United States when the terrorists killed the President, Vice-President, and all successors. He then appointed Miles Morales to join The Ultimates in the war. Spider-Man was a key member of the resistance, which eventually defeated Modi and Hydra.
Mysterio
The next battle for Miles Morales came in the 2021 series Spider-Men by Brian Michael Bendis and Sara Pichelli. In this series, Mysterio found a way to travel from the mainstream Marvel Universe to the Ultimate Universe. It was later discovered that Kindred allowed this to happen, and it resulted in Peter Parker from this world meeting Miles Morales for the first time.
This allowed the two Spider-Men to work together to battle Mysterio, who had attacked and killed The Kingpin to take his role as the main crimelord in the Ultimate Universe. The two Spider-Men beat him, and Peter gave Miles his blessing, which really solidified the new Spider-Man's status in Marvel comics.