[9] Pettas suffered his first professional loss on January 14, 2013, at Krush Grand Prix 2013, when he dropped a unanimous decision to Katsuya Goto.
[12] Pettas extended his winning streak to three consecutive fights at Krush.36 on April 1, 2014, as he beat Takeshi Watanabe by unanimous decision.
[13] Leona's three fight winning streak was snapped by Kotaro Shimano at Krush.39 on March 8, 2014, who stopped Pettas by technical knockout in the first round.
He won decisions against Tomohiro Kitai at Krush.41 on May 11, 2014,[15] Keisuke Nakamura at Krush.54 on May 4, 2015,[16] and Masahiro Yamamoto at Krush.56 on August 14, 2016,[17] and stopped Toshi with a head kick at Krush.46 on October 5, 2014.
[18] During this run, Pettas drew against Fumiya Osawa at Krush.44 on August 9, 2014,[19] and lost a unanimous decision against Haruaki Otsuki at Krush.50 on January 4, 2015.
[43] During his post-fight speech, Pettas called for a fight with the K-1 super featherweight champion Takeru Segawa, stating: "There are no Japanese fighters anymore [who could challenge him]".
[44] Petas faced the former K-1 Featherweight and RISE Bantamweight champion Yuta Murakoshi at K-1: K’Festa 3 on March 22, 2020.
[49] Pettas was finally booked to face the K-1 super featherweight champion Takeru Segawa at K-1 World GP 2020 in Fukuoka on November 3, 2020.
Due to his stature, particular skilleset and good run of form, Pettas was considered as one of the toughest challenges in Takeru's career up to that point.
[52] On October 9, 2020, it was revealed that Takeru had withdrawn from the bout after he had suffered a fracture in his left hand during training, and which would require surgery.
[55] Despite a good start to the fight which saw him successfully utilize his height and reach to outfight, Pettas was knocked down with a left hook in the dying seconds of the opening round.
[56] Pettas vacated Krush super featherweight title on September 3, 2021, with the intention of moving up to lightweight (62.5 kg).
[57] He faced Maki Chatchai, in a 61.5 kg catchweight bout, at K-1 World GP 2021 in Osaka on December 4, 2021.
[63] Pettas participated in the 2022 K-1 Super Featherweight World Grand Prix, held to crown a new divisional kingpin after the previous champion Takeru Segawa vacated the belt.
Pettas faced Ayoub Segiri in the tournament quarterfinals at K-1 World GP 2022 Yokohamatsuri on September 11, 2022.
[66] Petttas faced the Wu Lin Feng -60 kg champion Hirotaka Asahisa in the tournament final.
[68] Pettas faced the once-defeated WAKO Pro K-1 World Super Lightweight champion Rémi Parra in a non-title bout at K-1 ReBIRTH 2 on December 9, 2023.