Father from Fullmetal Alchemist. Sousuke Aizen from Bleach. Madara Uchiha from Naruto. These characters might seem different, but they have one very important thing in common - they're all totally OP anime villains.
Invincible anime villains must walk a fine line between creating meaningful challenges for the heroes to overcome and creating challenges that are actually impossible and require the heroes to go beyond the rules established by canon. When their defeats work, it's awesome - but when it doesn't, it can be a disaster. Still, it's always exciting to try and find out how seemingly unbeatable anime villains will finally bite the dust. Which ones are your favorites?
Father might have been defeated at the end of Fullmetal Alchemist Brotherhood, but it took hundreds of people to make it happen. Father isn't bound by the normal rules of alchemy - he can perform alchemy technique without paying any cost. Besides that, if he wants to understand something fully, all he has to do is touch it. When he absorbs the power of God into his body, he becomes so powerful that he can do literally anything he wants, even creating a miniature sun in the palm of his hand.
But Father's human body has trouble keeping up with all of that power. In order to boost his strength as he's being repeatedly attacked by the entire military and a whole bunch of other people who want him gone, he absorbs the homunculus Greed. Greed turns his body into a brittle substance, one that's easy to destroy with a single punch - which is how Edward Elric ultimately defeats him once and for all.
Ainz Ooal Gown might be the only character on this list who is actually unbeatable - and that's probably because he's a villain protagonist. As a guild master, he's considered the most powerful of the Almighty 41 Supreme Beings, for a variety of reasons. He's able to use a spell that gives him the strength of a Level 100 warrior, and he boasts countless other spells as well. He has his own pocket dimension where he keeps weapons and other items, he can use Super Tier Magic (a system of magic that does eveything from creating tornadoes to granting wishes) and he can use a variety of techniques that plow through his opponents' resistances to destroy them instantly. Will he ever be taken down? That remains to be seen.
As the king of the Chimera Ants, it goes without saying that Mereum would be ridiculously powerful. He's proud of his strength and thinks of those he says are beneath him as expendable fodder who he can destroy or even eat. He's so strong and fast that he was able to slap the heads off of multiple squadron leaders with his tail, moments after he was born. He's strong enough to punch through walls, and fast enough to move without anybody being able to detect it. He can survive poison, explosions, and go for at least six days without rest or food.
He's eventually taken out by the Poor Man's Rose, a chemo-explosive weapon. While he survives the initial impact, he succumbs to the poison it leaves him with. He passes away playing a game called Gungi with a young blind girl named Komugi - the only person he ever felt any genuine affection for.
Sousuke Aizen is not someone you ever want to find yourself fighting against, because he is not only ridiculously strong, he's also brilliantly manipulative. He spent years persuading everyone that he was a loyal and mild-mannered member of Soul Society, only to launch one of the most memorable betrayals in anime history. Not only is his physical strength off the charts, but Aizen can also do things like teleport, regenerate, and more. He can even take full control over all five of another person's senses, making it impossible for them to even begin to guess what he's doing or act accordingly.
He's ultimately defeated by Ichigo Kurosaki's use of a powerful attack called Mugetsu, which severely damaged him and forced him to regenerate to a weaker form. After that, Kisuke Urahara was able to seal his powers. Surprisingly, Aizen went willingly to prison after that, having changed his outlook on life somewhat by this point.