His first fight in 2010 Hari defended his Showtime heavyweight title with a second round knockout over Mourad Bouzidi.

In April Hari defeated Alexey Ignashov in the K-1 World Grand Prix 2010 in Yokohama. The fight went to decision, Hari's first non-knockout win in 3 years.

Hari's Showtime title was again on the line against Hesdy Gerges in Amsterdam in May. Hari dominated most of the first round, hitting Gerges many times and having him on the ropes. Despite this Hesdy surprised everyone on the night for taking the punishment and refusing to go down, he stayed on his feet and did not go down once. This frustrated Badr, who kicked Gerges in the face when he was trying to stand up after a slip leaving him lying on the canvas. Badr was again disqualified and did not speak in the ring after Gerges was announced the winner. Instead, training partner Melvin Manhoef apologized to the fans on Badr's behalf but was booed by the crowd who were more happy when Badr was disqualified and Gerges became the new "Its Showtime" Heavyweight champion

In May 2009 Hari fought Semmy Schilt in a long-awaited bout for the newly introduced It's Showtime World Heavyweight title. Hari came out very aggressively and knocked Schilt down twice in the first round. The fight was stopped after the second knockdown and Hari took the heavyweight title in 42 seconds.

At the K-1 World Grand Prix 2009 Final 16 Hari again used his trademark right body shot to score a first round knockout over Zabit Samedov.

At the selection for the K-1 World Grand Prix 2009 Final Hari chose to fight Ruslan Karaev for the third time. He ran through the tournament with first round knockouts over Karaev and Alistair Overeem in a rematch, to make it to the World Grand Prix Final for the second year against Semmy Schilt. In their rematch Hari lost by KO after being knocked down 3 times in the first round.

All of Hari's wins in 2008 were by knockouts, by beating Ray Sefo in Yokohama, Glaube Feitosa (whom he defended his heavyweight title) in Fukuoka and Domagoj Ostojic in Hawaii. On his next fight in Seoul he qualified for the K-1 World GP 2008 Final by TKO win over the Korean giant Hong Man Choi.

In the quarterfinals on December 6, Hari defeated three time K-1 World champion Peter Aerts by TKO in the second round. In the semis he knocked out Errol Zimmerman and headed to his first K-1 Final against Remy Bonjasky. After suffering a knockdown in the first, Hari was disqualified in the second round for unsportsmanlike conduct by stomping and punching an already downed Bonjasky. First the referee Nobuaki Kakuda issued a yellow card and one point deduction. Meanwhile Hari proceeded to Bonjasky’s corner shouting, and quarreled with his opponent's trainer Ivan Hippolyte who then also approached Hari aggressively, but the officials prevented any further physical contact between them.[7] After the five-minute recovery time elapsed, the doctor reported Bonjasky was seeing double and could not continue. Hari was issued a red card and Bonjasky was declared the K-1 World GP 2008 champion.[2]

In later interviews Badr claimed Bonjasky was acting, and that "Remy's corner was screaming at him to stay down".[8]

After the event Badr was not suspended for his actions, but K-1 has however stripped him of his heavyweight title and his fee for participation in the tournament.[9]

While there were many rumours of his and his opponent's participation, it was finally announced that Badr would face MMA Heavyweight Alistair Overeem in a K-1 rules match on K-1's NYE extravaganza. Hari lost the fight by a left hook KO in the first round within 2 minutes. Part of the fight agreement is that both Badr and Overeem would also fight each other in an MMA match for FEG's DREAM promotion sometime in 2009.

On April 28, at K-1 World GP 2007 in Hawaii, Badr Hari and Yusuke Fujimoto fought for the newly introduced Heavyweight belt. Hari won the fight in 56 seconds with a kick to the chin. With the knockout Hari became the world's first ever K-1 Heavyweight champion.[6]

Hari got his chance for revenge against Graham in Hong Kong where he dropped Graham with a body punch and won by unanimous decision.

On September 29, 2007 at the K-1 World GP 2007 Final Elimination, Badr Hari beat the K-1 World GP 2007 in Las Vegas tournament champion, Doug Viney, by a second round KO and qualified for his first K-1 World GP Final, held on December 8 in Yokohama, Japan. His winning streak came to an end with a decision loss to Remy Bonjasky, during quarter final.

Hari returned to the ring at the K-1 World GP 2006 Final Elimination in Osaka, Japan against Ruslan Karaev. Karaev hurt Badr with a straight right that left Hari slouching over in the corner, then Karaev delivered a kick to Hari's face when it looked as though Hari was already lying on the canvas. Hari was counted out by the referee but immediately he and his corner protested, saying the kick was a foul. When the referee did not respond, Hari left in anger and trashed his changing room.[4]

Despite being knocked out, Hari was once again picked as a reserve fighter in the K-1 Grand Prix 2006 Finals against Paul Slowinski. He won the fight by unanimous decision.

Hari then fought Nicholas Pettas at Dynamite and broke Pettas's left arm in the second round with his powerful round kicks.

Hari got his revenge against Karaev at the K-1 World GP 2007 in Yokohama. Karaev and Hari's matchup was one of two bouts to qualify for the first K-1 Heavyweight Title Match, scheduled on April 28, 2007 in Hawaii. Hari was knocked down in the second round and was just able to make it to his feet when Karaev intended to finish the fight with a swinging punch which Hari ducked, and landed a right cross to score a KO.[5]