In the world of anime, gods are typically the most powerful entities around - except for when they're defeated by a particularly dedicated anime character who doesn't care if they're dealing with an all-powerful deity.
Many anime characters who defeated gods are shonen protagonists like Naruto Uzumaki and Natsu Dragneel, who took on gods with the power of friendship and amazing powerups. Most are also mortal, which makes it that much more exciting when they manage to hold their own against a god. But a few are actually gods themselves, like Beerus from Dragon Ball Super, who erases Zamasu from existence like it's nothing, and Yato from Noragami, who struggles to defeat his former ally Rabo.
Which of these characters do you find impressive?
Kaguya Ōtsutsuki is a mythical being who is the source from which all chakra flows. Once, she loved humanity and was considered a benevolent deity, but she eventually began to see humans as a destructive force who had to be stopped. She believed that she should be the sole owner of all of the chakra in the world, and set about trying to reclaim it. She was eventually sealed away, but reappeared at the end of Naruto Shippudden as one of the series' biggest enemies.
After a long and grueling battle, Naruto, Sasuke, and Sakura perform a coordinated attack in which they seal Kaguya into the Ten-Tails, and then into the Demonic Statue, which was consumed by a truth-seeking ball. They also send Black Zetsu to the moon so that he won't be able to revive Kaguya in the future. It doesn't matter if you're a god, you can't beat a ninja in an orange jumpsuit.
Edward Elric is able to defeat Father, a homunculus who has acquired godlike powers, with the help of a wide range of allies - including, surprisingly, Greed, one of the homunculi that Father created. When Father absorbs Greed in an attempt to bolster his own strength, he ends up turning his formerly impenetrable flesh into grapheme. This makes it possible for Edward to beat Father into oblivion.
Both Beerus and Future Trunks manage to defeat different versions of the same god, Zamasu. Beerus isn't too thrilled with Zamasu's evil plan and attempt on Goku's life, so he uses his own powers as a god of destruction to erase him from existence. Because this happens in an alternate timeline, however, Zamasu still exists in another timeline - this time in a fused form. It's Future Trunks who manages to take out this version of Zamasu, and he does so by literally slicing him in half.
In one of the Inuyasha movies, Fire on the Mystic Island, Inuyasha and his allies head off to Horai Island, which has been cursed by the Four War Gods, who must be defeated in order to free the inhabitants. Sesshoumaru manages to take out one of the gods, while Sango and Miroku handle another one, but it's only Inuyasha who is able to take out two on his own. When the four gods are defeated, they combine to create the final War God, who Inuyasha and Kagome take on together. The island's inhabitants are now free from the gods' control.