Well.. I had to think again to (again) make a remake for the Negaduck pokemon team. And I succeeded! Now I'll explain why I chose them specifically:
According to my personal headcanons, Negaduck would have gotten it first. After a fierce battle, Sandslash would have chosen him and entered the PokéBall. His Sandslash would be just like its owner – prickly, silent, and wouldn't be afraid of Anti, but would instead be able to find a way to connect with him. A character like Negaduck doesn't need affection or love, but most importantly, loyalty, which Sandslash could provide.
Dragalge is a poisonous and dangerous Pokémon, and very aggressive at that. Knowing Nega's personality, he would certainly have been able to tame it, but again, not through care, but through its equally "poisonous" nature. Dragalge is not the majestic and kind dragon depicted in fairy tales, but a dangerous monster, which is why it has earned the villain's respect.
He found it when Grimmsnarl was still Morgrem. The Pokémon itself is distinguished by its cunning and marginal lifestyle, which would suit Nega's personality perfectly. Plus, Grimmsnarl is a rather strong Pokémon, which might also appeal to its "master."
4. Toxicity (Low Key Form)
I gave him his Low Key form because his Amped Form would have been too... noisy for Nega. He's energetic and doesn't know how to control his aggression, which would often hinder a villain in battles. This quieter form of this Pokémon, while no less honorable and dangerous, is perfect for Negaduck.
A poisonous snake Pokémon with an extremely aggressive, cruel, and cunning nature. It's obsessed with battle, intelligent, observant, and has no compunctions. Seviper is a literal reflection of Negaduck, who needs someone by his side who can understand his commands and moods without words or questions.
For the Negaduck, this Pokémon acts as a kind of "voice of reason" in the team. Ariados doesn't attack too conspicuously; rather, it will patiently spin its web until its prey is trapped, at which point it strikes. Such stealth and thoughtfulness would clearly please its "master".
As a result, Negaduck has a rather deadly, effective, yet loyal team to the trainer. Unlike the previous pack, these Pokémon would not be afraid of him, but would obey commands due to authority and silent mutual respect. Next, I plan to make either Megavolt or Bushroot, and you write how much you agree or disagree with my choice.