Objectively, Gellert Grindelwald actually had better "Dark Lord" achievements than Voldemort, despite being killed by him. Voldemort just happened to be eviler and more driven, hence more dangerous, but he is by no means more powerful than Grindelwald.
Grindelwald Is More Powerful and Cunning Than Voldemort
Grindelwald had more power in the Wizarding World up till the final moments of his life. He had more followers, and they were intensely loyal to him. He conquered more of the globe and could perform more advanced forms of magic.
Albus Percival Wulfric Brian Dumbledore was the only wizard Voldemort ever feared and the only one who could have defeated him in a duel. Albus Dumbledore is the most powerful wizard in the Harry Potter.
Dolores Umbridge. And in a twisted way, she could almost be seen as even more evil than Voldemort. Voldemort was obviously extremely evil, but he was also the type of evil that's easy to spot and the type of evil that's up front.
Voldemort is the most powerful wizard in all of Potterverse, past or present. Yes, yes, Dumby is wiser; Grindy is more strategic. But as far as raw power goes, Voldemort is untouchable. Voldemort led his own downfall and it was down to mere chance that Voldemort lost the First Wizarding War.
He was the Half-Blood Prince, as well as the maker of several powerful spells. Severus Snape might have pretended to serve Voldemort (while in fact, as we all know, working as a double agent for Dumbledore), but there's almost no question he was more powerful than the Dark Lord.
Besides Dumbledore, he is also the only wizard ever known to be able to apparate silently. Voldemort was also said to fear one wizard alone, Dumbledore.
Bellatrix Lestrange was Lord Voldemort's equal in cruelty, if not worse than him. She was unparalleled when it came up to committing some of the most horrible acts of cruelty and destruction. She truly belonged to the Dark side and loved to embrace it.
Voldemort's greatest fear is death and as a result a boggart takes the form of his own corpse. It is unsurprising that this is Voldemort's biggest fear. After all, he did split his soul up encasing it in various horcruxes just so to keep himself from dying.
Lord Voldemort (Ralph Fiennes), aka Tom Riddle, was described by Dumbledore as one of the best students ever to graduate Hogwarts as well as "the most dangerous Dark wizard of all time." Before he had even learned about the existence of the Wizarding world, he was terrorizing his fellow orphans with impressive but ...
Voldemort intentionally made six Horcruxes, but when he used Avada Kedavra on Harry, he unintentionally created a seventh Horcrux. Instead of dying, Lily's love for Harry created a counter 'curse' known as Sacrificial Protection and saved Harry.
His exceptional magical abilities, immense knowledge of various branches of magic, and strategic thinking make him a formidable wizard. Dumbledore served as the Headmaster of Hogwarts School of Witchcraft and Wizardry, was a highly skilled duelist, and possessed incredible wisdom and intuition.
The Horcruxes Left Him Vulnerable & Weak
Although they did give Voldemort another chance to join the living after his curse against Harry Potter rebounded, they harmed him in the long run.
We would have to give the victory to Darth Vader. While the two dark lords seem perfectly matched on their villainy and power, Darth Vader's lightsaber and ability to immediately use the force to choke Voldemort, without chanting any spell would end this showdown in seconds.
The Killing Curse was created in the early Middle Ages by Dark witches and wizards. Primarily, the curse was used to quickly slay opponents during a duel.
Voldemort's weaknesses are arrogance, aforementioned fear of death, and total disregard for things that he does not understand, all of which eventually contribute to his downfall.
Peter Pettigrew
He definitely ranks at the top of those who should be regarded as the most evil members of the Death Eaters, if for no other reason than that he was more than willing to betray Lily and James to their certain deaths at Voldemort's hands.
Albus Dumbledore
It is not certain what the specific fear is as he is not fearing the death of his sister as she is already deceased and it is suggested that Dumbledore fears that it was him who directly killed his sister in the conflict or that he fears the loss of control that lead to his sister's sudden death.
Even when battling Voldemort, in Harry Potter and the Order of the Phoenix, Dumbledore never uses lethal magic. In the duel, Dumbledore is definitely on par with Voldemort, and Voldemort is seen to be annoyed that he can't overpower Dumbledore.
He hated his father for being a muggle, leaving his mother and her heritage, etc. Voldemort hated Dumbledore because he (Dumbledore) was his (Voldemort's) rival. Voldemort hated (or more feared and disliked) Harry because he (Harry) was his doom.
Minerva McGonagall
To be fair, it was McGonagall, Horace Slughorn, and Kingsley Shacklebolt who dueled Voldemort at the same time. Sadly, he incapacitated all three of them after being enraged at the news of Bellatrix Lestrange's death.
Of the characters in the books, the top-tier wizards are pretty clearly shown to be Dumbledore, Voldemort, and Grindelwald. If one accepts that magic has advanced since ancient times, these three are probably even greater than the Hogwarts Founders themselves.
During his final confrontation with Voldemort, Harry knew that he (Harry) was the Elder Wand's true master. He again cast Expelliarmus, ejecting the wand from Voldemort's hand into his own as the Killing Curse rebounded off his body, fatally striking Voldemort.