Max Tennyson (Classic)/Alien Force

In Ben 10 Returns: Part 1, he left a holographic message for Ben, stating that he was investigating renewed alien activity on Earth and claims that he had the Omnitrix.
In Max Out, Max destroyed a Xenocite hatchery by detonating a Null Void Projector, which, after removing its focusing lens, made a "pretty good imitation of a hand grenade" and produced an explosion that covered over half a mile. Max appeared to have been killed in the blast but was instead sent to the Null Void, where he, calling himself "the Wrench", fought Dr. Animo, who was calling himself "D'Void". 
Max appeared in War of the Worlds: Part 1 and Part 2 to aid Ben in his battle with the Highbreed, along with the Plumbers' Helpers. After the Highbreed left Earth, he took the Helpers under his wing as his apprentices. 
Max and the Plumbers' Helpers appeared in Vengeance of Vilgax: Part 1 and Part 2. They helped fight Vilgax but were all beaten by him. After Ben beat Vilgax, he tells his old nemesis to never return.
In If All Else Fails, it was revealed that the Highbreed had infected Max with a dormant seed, which was part of a failsafe plan of the Highbreed. It is mistakenly activated by a Highbreed officer, who was unaware that the Highbreed had called off the war. Max was freed from the seeds' control by Ben, Gwen, and Kevin.
In Above and Beyond, Max set up a scenario in which Ben was to go on a rampage on board an orbiting Plumbers' Research Satellite Delta. He then called the Plumbers' Helpers to come and save him. They managed to defeat Ben, but the battle had caused the space station to fall out of orbit towards the city of London. The Plumbers' Helpers decided to activate the station's self-destruct, which would mean sacrificing their lives in the process. However, the space station didn't explode. Instead, Max appeared along with Ben, who revealed to the Plumbers' Helpers that the space station was a Plumber training facility and that Ben's "rampage" was set up to test them. Max also stated that by putting "the safety of others ahead of their own lives", the Helpers would be admitted to Plumbers' Academy.
In The Final Battle: Part 1 and Part 2, Max took part in the fight against Vilgax. When Kevin returned to his human form, Max stated that the Omnitrix kept him in his mutated form. Max aided Gwen in trying to stop the ship from crashing into Bellwood. After Ben escaped from Vilgax, he, Gwen, and Kevin shared a group hug with Max.