system
Given the following post, respond as if you're commenting on Reddit:
human
[harry potter] nowhere in the world, was there a wizard (or a group) strong enough to defeat voldemort?
gpt
In a contest of Magical Skill? No, there wasn't.

Voldemort was the most dangerous, if not the most powerful wizard in the world, with his closest equal being Dumbledore, who himself considers Voldemort to be superior, despite him wielding the Elder Wand. 

This means a lot, since Dumbledore was established as the only Wizard in the world capable of defeating the Dark Wizard Grindelwald, despite Grindelwald being the wielder of the Elder Wand then.

As for a group of powerful wizards ganging up on him, that would almost certainly end in failure. During the Battle of Hogwarts Voldemort has shown himself capable of defeating a larger number of poweful opponents, when he was easily keeping up with duelling Slughorn, Kingley and Mcgonagall at the same time and winning, despite Voldemort wielding a unfitting wand and his opponents being protected by the magic of Harry's sacrifice, which is the only reason they survived the fight.

Despite this Voldemort is also extremely cautious, showing himself unwilling to engage powerful wizards in battle, without sufficient preparation unless absolutely necesarry.

Like he showed himself completely unwilling to actively engange Dumbledorein Battle, despite Dumbledore considering himself weaker and the one confrontation we see between them almost resulting in Dumbledore's Death, if his phoenix didn't take a killing curse for him. He also immidiately left their duel when Aurors were about to arrive, since they could actually give Dumbledore an edge. 

Likewise he refused to engage  Scrimgeour(the Minister for Magic and previous Head of the Auror office) in a fair duel and instead made sure to have his Death Eaters use the imperius curse to take control of the Head of the Ministry Departments first so they can surround Scrimgeour with their own people before Voldemort strikes.

We also know that he often just assassinates powerful wizards in their own homes without really giving them a chance to fight him, like he did with James Potter who didn't even have a chance to reach for his Wand or Amelia Bones(the Head of the Department of Law enforcement).

According to Hagrid Voldemort has also killed several of the most powerfull living wizards during the Last War.