Bowser

King Bowser Koopa, also known as Bownser, is the main antagonist of the Mario series. He is the King of the Koopas and the bouncer of the Villain Pub.

Early Life
Bowser has had a feud with the Mario Bros. ever since they were babies. When Mario and Luigi were born, Bowser's caretaker Kamek learned that the Mario Bros. were destined to destroy the Koopa clan. She set off to capture the Mario Bros. from the stork that was to deliver them, but only managed to capture Luigi and the stork. Mario, landing on Yoshi's Island, encountered the Yoshi clan, which carried him as they worked together to stop Bowser and rescue Luigi, succeeding in the process. However, the stork delivered the Mario Bros. to the wrong house, so the stork set off to deliver the Mario Bros. to their real parents. Kamek, seeking revenge, attacked the stork, still capturing Luigi and the stork as Mario reunited with the Yoshi clan on Egg Island. Bowser had captured Egg Island as his own, so the Yoshi clan once again carried Mario on their mission to stop Bowser once more, assisted by a disguised future Mario. After defeating Bowser and his future self, the Yoshi clan reunited the Mario Bros., and the stork delivered them to their real parents at last.

Over the years, Bowser has had many conflicts with Mario. Having set his sights on the Mushroom Kingdom, Bowser has hatched countless plots to take over the kingdom with his Koopa army, his son Bowser Jr., and his mercenaries the Koopalings, often doing so by kidnapping its princess, Peach Toadstool. Every time, Mario always foils Bowser's schemes, but Bowser always has another plan coming. Whenever the Mushroom Kingdom is faced with threats besides Bowser, he has also occasionally sided with Mario to stop the new threat. Bowser also has joined Mario and company in friendly activities such as go-kart races and sports.

How Super Mario Should Have Ended
Bowser has a staff meeting with a Goomba and a Bullet Bill. He explains that Mario has been an enemy of the Koopas, destroying their buildings and structures and literally stomping on them. His attempts at "kidnapping" Peach are him trying to strike a peace core with her, but they are usually fruitless in his favor. Having realized that Mario is impossible to kill, Bowser suggests a different approach. Under Bowser's orders, the Goomba and Bullet Bill set up a Warp Pipe to Aperture Science Labs, disguising it as a portal to Awesome Town, which works.

Villain Pub
Bowser serves as the bouncer of the Villain Pub, and thus enforces the pub's rules. Bowser has apparently been working for the Villain Pub since at least 1989.

To Battle!
Bowser halts a battle between a Xenomorph and a Predator before throwing them out, reminding them that the pub allows "boss battles only."

To the Tailor!
When Trevor Slattery arrives at the pub, Palpatine orders Bowser to take him out. However, as Slattery pleads for Bowser to let him in, Bowser accidentally stains Loki's suit.

The Boss Battle
Bowser is the first to be taken out by Batman, who drags Bowser out of the pub and beats him up.

How Age of Ultron Should Have Ended
Bowser is present as Ultron explains that he distracted the Avengers. The remains of Sokovia crash onto Earth and obliterate the pub, Bowser included. However, Superman averts Bowser's death by rotating the Earth.

How Suicide Squad Should Have Ended
When the Suicide Squad visit the pub, Palpatine has Bowser throw them out for being heroes.

How Infinity War Should Have Ended
When Thor accidentally snaps his fingers with the Infinity Gauntlet, Bowser is among the Villain Pub's slain members. He calls out to Palpatine, referring to him as "Boss," before fading away.

Power and Abilities

 * Fire Breathing: Bowser's most prominent and consistent ability, appearing in nearly all games he has been featured in. He can breath continuous streams of fire, or shoot blasts or flurries of fireballs at his foes. In some games, like Super Mario World and New Super Mario Bros U, he can make it "rain" fire blasts, and, in Super Mario 64 and New Super Mario Bros., he can also shoot blue fire blasts that can home in on Mario. His fire breath is apparently so hot that it is also just as effective underwater as it is on land.
 * Superhuman Qualities: Over the years, Bowser has displayed countless feats that put him far above the average person.
 * Superhuman Strength: Bowser's raw physical strength is frequently seen as one of his main powers. He can smash through boulders, lift immensely heavy objects with relative ease, and topple enemies numerous times his size. In many of the RPG and sport games, is typically among the strongest characters in the game, like in Super Paper Mario, where his attack stat is twice that of Mario, Luigi and Princess Peach's respectively. Much like with his fire breath, Bowser prides himself on his strength and frequently incorporates physical attacks into his fighting because of this.
 * Superhuman Durability: Bowser has proven time and time again that he is not taken down very easily by most foes. He can endure a seemingly endless amount of punishment, and somehow always returns from this in one way or another. He has been drenched in lava, electrocuted, blown up, crushed by objects as heavy as his own castle numerous times, fallen hundreds of feet, and even squashed by a T-Rex in Mario's Time Machine, and has inevitably survived each fate. In Super Paper Mario, after he seemingly sacrifices himself by holding up the ceiling of Count Bleck's Castle with O'Chunks, Luigi encourages the Princess and his brother to not give up hope on him by saying that he's survived far worse.
 * Superhuman Speed and Agility: Although his speed is hardy consistent between games, in some of his appearances, Bowser is shown to be a a capable runner and quite agile for his size. In Mario & Luigi: 's Inside Story, uses a treadmill placed by Fawful and Midbus to burn off thousands of calories gained by eating incredibly unhealthy food in only a few seconds.
 * Superhuman Stamina: Bowser's stamina is almost as limitless as his durability. He rarely ever shows signs of tiring, even when massively expending himself for hours on end. In battle, never slows down, keeping up with Mario and other enemies like his dark counterpart Dark blow for blow.
 * Dark Magic: While not as prolific in the use of it as Kamek, Bowser is well versed in using various forms of Dark Magic against his opponents. He apparently knows spells that can transform people into inanimate objects, as explained in the manual of Super Mario Bros. and he has used different magical wands over the years for varying purposes (although this is more commonly seen in the cartoons and comics).
 * Size Manipulation: In numerous games, Bowser has the ability to transform himself to a giant size to battle his enemies. Most of the time, he is empowered by Kamek or somebody else, but, as seen in Bowser's Inside Story, if he is super charged with adrenaline, he can temporarily achieve his giant size naturally. In the Super Smash Bros. series, by breaking a Smash Ball, he can become Giga Bowser, an alternate yet still effective version of his typical giant form. Regardless of how he gains it, his giant form massively increases his strength, durability, and other abilities, to the point where Mario and other characters cannot fight him directly, and must find some other way to defeat him. In games such as Paper Mario and Super Mario Galaxy 2, Bowser can use the power of Stars to grow himself to immense size.
 * High Skill in Sports and Other Activities: Like almost all Mario characters, Bowser is an extremely qualified player in numerous sports and physical activities. While not being particularly talented in any activity, he has been shown as a skilled tennis, soccer, hockey and basketball player, golfer, go-kart racer, Olympic athlete, wrestler (given some of his moves in the Smash Brothers games), and even a professional dancer.

Trivia

 * Bowser is fully voiced in "How Super Mario Should Have Ended," like in Super Mario Sunshine. However, in his other appearances, he instead communicates in grunts and speech bubbles, akin to most Mario games.