Reiner from Attack On Titan is one of the top ten graduates of the 104th Training Corps. He is not just a trained fighter; like Eren and other characters, he also has a Titan form. Reiner can transform into the Armored Titan, which has regenerative abilities, enhanced strength, and armored skin that can help him endure heavy attacks.
However, other anime characters could beat him in battle, despite him having these abilities. From Azusa and Shin's overpowered magic to Gon and Kirito's quick-thinking and agility to go with it, these characters could easily match him in battle regardless of which form he takes.
10 Gon's Speed & Usage Of Nen Could Overwhelm Reiner (Hunter X Hunter)
Gon is small and speedy, which could help him get around many of Reiner's attacks. Since Reiner is also slower in his Titan form, Gon could potentially get many attacks in before Reiner has a full chance to strike. Even though Reiner does have regenerative abilities to help him recover, Gon can use Nen to help take him down sooner rather than later.
Additionally, if Gon were in his adult form, he would be much harder to beat in general and it would help him unleash his full power against Reiner.
9 Azusa Could Use Magic To take down Reiner (I've Been Killing Slimes For 300 Years & Maxed Out My Level)
The overpowered isekai protagonist Azusa from I've Been Killing Slimes has more than enough magic to take down Reiner herself. As one of the strongest characters from her respective series, she can create new spells to adapt to new situations, fly, take down foes and enemies with magical barriers and use other offensive spells.
Considering that she could defeat the likes of demons like Beelzebub and the Demon King Pecora, Azusa could use her magical powers to take down Reiner regardless of which form he uses. She might not be as advanced with weapons like he is, but her magic would easily overcome those obstacles.
8 Cosette Could Use Her Musical Abilities To Shoot Down Reiner (Takt Op. Destiny)
Cosette from Takt Op. Destiny is powered by classical music. Provided that there is a piano nearby that Takt can play to activate her powers, Cosette could transform into her Musicart form and start shooting down Reiner on the spot. She can fire lasers, wield a giant sword to slash down foes, and she is extremely fast and agile with her movement.
Not only would this help her take down Reiner as a normal person, but she can use these same powers to get around Reiner's regenerative abilities. Her attacks would be fast enough to barely give Reiner the chance to recover, and so she could destroy him sooner rather than later.
7 Edward Elric Would Use His Alchemy To Take Down Reiner (Fullmetal Alchemist)
Edward Elric from Fullmetal Alchemist could use his alchemy to take down many foes, including Reiner. Since he can use his alchemy without a transmutation circle, this makes it easy for him to use his alchemy anytime and anywhere he wants. He could use these abilities to disable Reiner's weapons and fight hand-to-hand with him easily.
Edward might have a bit more difficulty taking down Reiner in his Titan form, but if Edward could defeat the likes of Father and other foes from his respective series, he can take on Reiner in battle and win.
6 Sugar Could Turn Reiner Into A Doll Regardless Of Size (One Piece)
Sugar from One Piece ate the Devil Fruit Hobi Hobi no Mi. This enabled her to turn people into dolls and erase memories of their existence from other people. It also gave Sugar eternal youth, which means that she would look like an unsuspecting little girl to Reiner if he ever met her. This would allow her to get the one-up on him, turn him into a doll, and promptly use him for her purposes.
Even if Reiner was already in his Titan form, she could still use her powers on him and there would be no way for him to stop her.
5 Kuro's Presence Alone Could Potentially Kill Reiner (Restaurant To Another World)
Despite not showing her powers off in the anime adaptation of Restaurant To Another World yet, Kuro is well-known for being a black dragon. She is so powerful that she had to exile herself to the moon so she would not accidentally destroy the world she lived in simply by her presence alone.
Thankfully, since she only works at the Western Restaurant Nekoya on Saturdays, she does not risk destroying her employment by accident. Considering her destructive power, she could kill Reiner by being physically present near him.
4 Sebastian Michaelis Would Take Reiner's Soul Eventually (Black Butler)
Sebastian Michaelis is a deadly butler who is also a demon. He could potentially make a Faustian contract with Reiner to work with him to an extent, only to take his soul later. Whether Reiner is a regular human or in his Titan form, there is nothing Reiner could do to counteract that.
Even if both of them met in battle, Sebastian could kill Reiner with anything he could get his hands on, cutlery included. It is also virtually impossible to kill Sebastian except with specific weapons, and Reiner has access to none of these particular weapons either.
3 Kirito Would Use His Excellent Swordsmanship To Destroy Reiner (Sword Art Online)
Kirito is an excellent swordsman and a strategic warrior overall. Considering his overpowered protagonist status, he could beat Reiner normally in battle with his agility, speed, and quick thinking.
Kirito might have a harder time beating Reiner if he transformed into his Titan form, but he would eventually defeat him thanks to his great strategies. Kirito's vast experience fighting floor bosses in Aincrad and other foes would help him adapt to fighting against Reiner's Titan form and beat him.
2 Sailor Moon Is Extremely Overpowered With Multiple Magical Abilities & Forms (Sailor Moon)
Sailor Moon is extremely overpowered with her many magical abilities and forms from the titular series. She alone could defeat Reiner regardless of which form he takes. She might not use advanced weaponry as he does, nor does she have air force training, so she might have some difficulty in aerial combat.
However, the rest of her magic abilities would make up for this, and she could easily destroy him with one of her ultimate attacks to finish him. Even if she does end up in a pinch, she could easily get the aid of her fellow Sailor Scouts to finish him for good.
1 Shin Is Another Overpowered Magic-User That Could Destroy Reiner In Battle (Kenja No Mago)
Shin is an excellent magic user, even if he is fairly overpowered from the beginning of Kenja No Mago. Even though he lacked common sense, he made up for it with his vast magical power. He was able to destroy most of the training room and the targets alone with one spell during his entrance examination and passed it with flying colors.
He can also use his defensive magic to enhance his clothing to protect himself. These spells could help him face off against Reiner and win the battle in the end, even if he does not know modern-day technology.