Despite being sidelined for a year with his first concussion early in training in 2000, he resumed his training in 2001 and was able to officially begin his wrestling career in 2002. He spent the next three years working under his real name as one of the young lions of the two Ohio-based wrestling companies under whose schools he trained, the Heartland Wrestling Association and the Northern Wrestling Federation. In October 2005, he found himself wrestling at the National Wrestling Alliance's annual convention, drawing the NWA's interest and being invited to further his training at their Los Angeles dojo and begin working for NWA on the West Coast. He accepted, starting with NWA at the beginning of the new year.
Allegra was soon repackaged as "The Machine Gun" Karl Anderson, a distant relative of Arn Anderson's kayfabe wrestling family, as they felt he had an "Anderson style" to his work. The Anderson family association was gradually dropped as he came into his own as a wrestler. By 2007 he formed a team with "Magnum" Joey Ryan called "The Real American Heroes", and outside the NWA began working for Pro Wrestling Guerilla and picking up big victories over the likes of Frankie Kazarian and Colt Cabana.
In early 2008, the NWA developed a new talent exchange agreement with New Japan Pro-Wrestling, leading to Anderson traveling to Japan in March to replace Yuji Nagata in the New Japan Cup. Despite being booked to lose his first match, his performance impressed NJPW officials so much they offered him a one-year contract, which soon came with a spot as a midcard worker in their Great Bash Heel stable, eventually becoming the regular tag team partner of fellow stablemate Giant Bernard, previously known as WWF/E midcarder Prince Albert/A-Train. In 2009, sometime after nearly all of GBH trading in Togi Makabe and Tomoaki Honma to become Chaos with Shinsuke Nakamura and Toru Yano, Anderson and Bernard became known as Bad Intentions and began challenging frequently for the IWGP Tag Team Championship. However, it wasn't until after getting kicked out of the stable altogether and turning face that they successfully captured the titles, held them for over a year and a half, and became arguably the greatest gaijin tag team in New Japan's history. Shortly after their reign ended on the January 4 Wrestle Kingdom show in 2012, Bernard left NJPW to return to WWE.
On his own, Anderson's star only ascended further, reaching the finals of various tournaments in 2012 and even winning the World Tag League as part of the tag team Sword & Guns with Hirooki Goto. However, through 2012 and 2013, his attempts to challenge after IWGP Championships such as Hiroshi Tanahashi's IWGP Heavyweight Championship and the Killer Elite Squad's (Davey Boy Smith Jr. and Lance Archer) IWGP Tag Team titles, always came up short. It was the green light for a behind-the-scenes friendship to become a collective heel turn and faction on-screen that allowed Anderson to become a part of history, when May 3's Wrestling Dontaku saw Anderson and Tama Tonga join Prince Devitt and Bad Luck Fale in their attack on Tanahashi, officially founding the force that would become known as Bullet Club.
Despite the Club being centered around Devitt as the leader, Anderson quickly became the group's main handler of the microphone, and both men had their turns going after what was now Kazuchika Okada's IWGP Heavyweight Championship. For the G1 World Tag League that year, Anderson brought in Doc Gallows, a big man known for his stints in WWE and TNA, to be his tag team partner. Instant chemistry and success followed, as Anderson and Gallows won the 2013 World Tag League tournament, then went on to beat KES at Wrestle Kingdom VIII to become IWGP World Tag Team Champions. When Devitt left NJPW and was replaced by AJ Styles at the April 6, 2014 Invasion Attack show, Anderson was considered by NJPW to be the official leader of Bullet Club despite Styles becoming its most elite wrestler, effectively forming a Big Bad Duumvirate. Throughout the next couple of years, Anderson and Gallows would gain back and lose the IWGP Tag Team titles three times and Anderson would remain the primary voice and co-leader of Bullet Club along with Styles as it soared in popularity both in its native Japan and especially in many of its members' homeland in the United States. In February 2016, Anderson left NJPW with Gallows, a month after Styles had gotten kicked out of Bullet Club to do the same, ceding full leadership of the group to Kenny Omega.
Anderson debuted in WWE with Luke Gallows eight days after WrestleMania 32, and very quickly they made their intentions known: to reform their alliance with AJ Styles and take over WWE. Styles took some convincing initially, but eventually he agreed. Taking over, however, was a different story. While he and Gallows did win the WWE Raw Tag Team Championship twice, their WWE run is mostly considered less impressive than their NJPW run as they failed to establish a dominant force before being ultimately released in 2020 due to WWE having to downsize as a result of the COVID-19 pandemic shutdowns.
Following their departure from WWE, Anderson and Gallows began teasing joining numerous companies, Anderson's primary focus being on a return to NJPW, before The Good Brothers revealed in the summer that they'd signed with Impact Wrestling on a two-year deal that would allow them to also sign part-time with NJPW once borders were open.
"THE MACHINE TROPES!":
- Action Dad: Has four children with his hot Asian wife.
- Affably Evil: He may be a loud and coarse individual who revels in kicking ass by hook or by crook, but damn if he isn't one of the coolest guys to do it.
- All-American Face: The Real American Heroes were an arrogant villainous parody of this, especially during their feud with Los Luchas.
- The Real American Heroes had rivalries with The Young Bucks, oddly enough, in both NWA and PWG.
- Suzukigun's Killer Elite Squad were this for him as a tag team wrestler in NJPW.
- As a singles wrestler, Anderson shared the same competitive hatred for Okada, Tanahashi, and Nakamura that his fellow BC leaders have had.
- The Usos, The New Day and The Viking Raiders are quickly becoming this for him and Gallows in WWE.
- Badass Biker: The Bullet Club is heavily inspired by this trope and his tag team partner basically is one.
- Badass Longcoat: Rocking them in his entrance gear since 2016, through Wrestle Kingdom 10 and into his WWE career. Went back to T-shirts and regular-length vests again by mid-2017.
- Bald of Evil: He's usually a heel, and he's been bald since '07.
- Bash Brothers:
- With Joey Ryan in NWA.
- With Giant Bernard early in NJPW.
- With Luke "Doc" Gallows later in NJPW and then again in WWE.
- Beard of Evil: He's usually a heel, and rocks a tight beard.
- Big Bad Duumvirate: Was part of this with AJ Styles from 2014-2016. Styles may have been the highest elite wrestler, IWGP Heavyweight Champion, and general guy to beat, but Anderson was the go-to voice for promos and had seniority as one of Bullet Club's co-founders as well as The Dragon to the original leader. If you asked fans, ROH, or NJPW who the leader of Bullet Club was at the time, you're as likely to get one answer as the other.
- Crowd Chant: Aside from the Bullet Club name itself, which is pretty much chanted everywhere the group or its remnants are, he's had his promos interrupted by "Fuck TNA" chants at ROH events, such as War of the Worlds. This isn't hostile, mind you: it's said fully in support, since Bullet Club was responsible for "bringing back" AJ Styles and The Young Bucks from that promotion.
- The Dragon: To his best friend Prince Fergal Devitt in the first year of Bullet Club.
- FaceHeel Turn: Like the rest of Bullet Club's co-founders and many of its members who joined afterward, Anderson was a face prior to becoming too sweet.
- Facial Markings: Occasionally sported these to complement Gallows.
- Finishing Move:
- Gun Stun (cutter/stunner) in NJPW, sometimes done from the second rope as Swivel Gun Stun.
- The Baddest Kick in the World (running big boot) as Chad 2 Badd.
- Rocket Kick (running single leg front dropkick) in WWE. This was a Signature Move beforehand.
- Used an Arn Anderson-style spinning spinebuster in the NWA. This later became a Signature Move.
- With Doc Gallows he's got the Magic Killer (an aided whiplash neckbreaker) and the Boot of Doom (Rocket Kick combined with Gallows' fireman carry flapjack), though the latter has yet to score a pin in a match and is usually used to take down guys in out-of-match fights.
- Foreign Wrestling Heel: For about 2½ years at least in Japan.
- Gun Nut: Has his own gunfire sound effect, has a taunt where hes pretending to fire a machine gun, sometimes brings a life-like toy machine gun to the ring with him and two of the partnerships he joined are called Sword & Guns and Bullet Club.
- HeelFace Revolving Door: In 2015, Anderson was one of many Bullet Club members who found themselves working traveling back and forth between Japan and the US, working heel in New Japan, face in ROH and US independents feds, so on and so forth.
- A Hero to His Hometown: Replace "town" with "country" and see above.
- Heterosexual Life-Partners: Is this with Devitt, Gallows, and Styles in Real Life.
- He Who Must Not Be Seen: Karl Anderson has a hot Asian wife. He constantly references her in promos, interviews, and the Talk'n Shop podcast. Yet she's never been seen anywhere in social or wrestling-related media, as he generally believes in maintaining the mystique surrounding his wife as opposed to thrusting her directly into the limelight, so you almost have to take his word for it. Or at least you had tountil May 26, 2016 happened on Twitter:@mcgrillen: @KarlAndersonWWE please prove you have a hot asian wife...@mcgrillen: @KarlAndersonWWE legend...well played
- Jerkass: If you're not in his crew, he's mean to you and proud of it.
- Large Ham: Get him talking freely, he is one of the most boisterous and animated guys in any room.
- Lightning Bruiser: Speed and agility, understated power, good in a fight; yep, he qualifies.
- Mr. Fanservice: He got ripped abs in 2018. Expect him to show them off.
- Names to Run Away from Really Fast: You don't get to call yourself Machine Gun and have it stick for over a decade without being a dangerous man.
- Only in It for the Money: He came to WWE to make money, win titles, and beat the crap out of people. He and Gallows call it "being mean and making green."
- Power Stable: G.B.H., Chaos and Bullet Club in New Japan.
- Power Trio: With [AJ Styles/Finn Bálor] and Luke Gallows in what WWE simply calls The Club/Balor Club/The OC.
- Put on a Bus: Kayfabe-wise, he and Gallows' failure to protect AJ Styles from getting buried by The Undertaker completely dashed all hopes of their covenant taking over WWE, so they quietly left. In reality they were furloughed due to massive budget cuts related to the COVID-19 shutdowns, particularly after Vince was forced to shut down the XFL at a loss even quicker than the last time.
- Red Baron: "2 Badd" as Chad Allegra. "The Machine Gun" and "The Toughest Man in the Building" as Karl Anderson.
- Red Oni, Blue Oni: Was usually the Blue to Doc Gallows as the "A Team", though occasionally he was the Red to AJ Styles instead.
- Anderson acknowledges that the various Kliq-inspired gestures he and other Bullet Club members did was a deliberate homage to the Kliq and its spinoff stables, D-Generation X and the New World Order.
- Combined with Take Up My Sword: Anderson and Gallows' Magic Killer finisher is a carry-over from Anderson's tag team with Giant Bernard as Bad Intentions, which in turn is a carry-over from Bernard's tag team with Travis Tomkonote as well as Tomko's TNA team-up with AJ Styles at the same time.
- Show Some Leg: Was frequently susceptible to this during the Bullet Club vs. Kingdom feud. Despite frequently acknowledging his hot Asian wife and at times being accompanied by Gallows' wife Amber, he couldn't help but take notice whenever Maria Kanellis got on the apron and started seductively gyrating.
- Sir Swears-a-Lot: When talking off the clock or especially in New Japan. He and Doc together could turn a Swear Jar into a gold mine.
- Toxic Friend Influence: He and Gallows are portrayed as this in WWE. They actively provoked AJ Styles to both of his heel turns in WWE, and despite the brief Bálor Club alliance in 2018 being their HeelFace Turn it was also the closest that Finn came to being a heel prior to returning to NXT in late 2019. Furthermore, going by the subtle off-mic interactions with both Bálor Club and The OC, Anderson seems to be more of the right hand man advising or encouraging the central singles star as to how to move forward, while Gallows is the hotheaded enforcer more than happy to bring the muscle to the table.
- True Companions: With most of his other Bullet Club stablemates, as well as Giant Bernard. In Real Life this also extends to other prominent members of the New Japan roster in his time there, including Chaos's Rocky Romero, with whom he and Gallows hosted a podcast called Talk'n Shop. And if anyone doubted he was this with his larger good brother, he confirmed it when he named his fourth child Cash Gallows, with Isaiah Cash being the big man's Ring Ka King ring name.
- Unrelated Brothers: Karl Anderson was originally packaged by the NWA as a distant relative of the Anderson family, almost none of whom are related to each other in real life. Since he didn't like using the Anderson gimmick as a crutch, this was largely phased out after a few years, with the most common reference now being that he reminds some people of Arn Anderson.
- Worthy Opponent: Hiroshi Tanahashi considered him this in 2013, at least before he turned back heel.
- Would Hit a Girl: Despite being attracted to her, Anderson and company was perfectly willing to take out Maria Kanellis when she got too involved in their business during the Kingdom feud.