Obi Wan Kenobi perfectly summed up Darth Vader’s two primary weaknesses when he described Vader as “more machine now, than man, twisted and evil.” Those weaknesses: technology, and himself.
Vader is entirely reliant on a mechanical suit to survive. Thus, he’s susceptible to attack by electricity (his ultimate undoing coming by virtue of the Emperor’s Force lightning in Return of the Jedi).
And that suit is run by battery; if Vader is separated from a power source long enough, his life support and mechanical systems would ultimately fail.
Vader, though mostly machine, is still man, though. Anakin Skywalker’s worst attribute was only augmented when he became Vader: Rage.
Nothing stood in Vader’s way, from Sand People to Imperial officers that failed him. But… that rage made him lose control and waste energy. If you could enrage him, and survive long enough to exploit that weakness, you might be able to defeat him as Kenobi did on Mustafar.
To see the full list of Vader’s strengths and weakness, pop over to Screenrant, here: