On 27 August 2012, Katidis signed a four-year contract with AEK Athens which would keep him at the club until 2016. AEK Athens and his former club Aris agreed on a €100,000 transfer fee. Katidis created an international controversy on 16 March 2013, when he gave what appeared to be a Nazi-style salute after scoring the winning goal against Veria. His action drew condemnation from politicians, fans and the media. He later told the public he was unaware of the gesture's connotations, stating that he just wanted to dedicate the goal to a colleague in the stands. AEK coach Ewald Lienen remarked that Katidis "doesn't have an idea about politics". As a result of the salute, the Hellenic Football Federation voted unanimously to give Katidis a lifetime ban from all Greek national teams and he was fined €50,000. He was furthermore suspended by AEK for the rest of the season.
Italian Serie B side Novara signed Katidis. Novara's owner Massimo De Salvo said that they would not be 'playing down' the incident. "We don't have the intention to play down his gesture," he said. "It was disrespectful to the millions of people that suffered and paid with their lives for those who believed in false ideals and myths." Salvo also said Katidis' remorse was a key factor in beginning negotiations with the 20-year-old. "We want to give him another chance, because we believe that making such a mistake is serious, but acknowledging it is worthy." The Italian media have dubbed Katidis the 'Greek Di Canio', referring to the former Sunderland manager Paolo Di Canio, who caused controversy as a Lazio player celebrating a goal by giving a Nazi salute. Eventually Katidis signed a 1+1 year contract with the club. On 31 July 2014, Novara announced the end of cooperation with the player.
Veria
After being away from Greece for a year, Katidis returned to his home country by signing a two-year contract with Veria. Giorgos made his official debut on 20 September 2014 in an away loss against Olympiacos in Pireaus. He made his second appearance against Ermionida in the Greek Cup. He made his third appearance as a substitute as he replaced Sotiris Balafas against PAS Giannina. On 26 January 2015, Katidis was released by the club as he didn't impress with his performances.
On 29 January 2015, Katidis penned a 2½-year deal with fellow Superleague Greece side Levadiakos. He made his last appearance with the club in a 1–0 away loss against PAOK.
On 30 January 2017, Katidis signed a season contract with the Finnish club FF Jaro. On 4 February 2017, in his first match with the club, this year's most controversial acquisition of Finnish football has presented itself, as Katidis was involved in FF Jaro goals by giving the two assists in a sensational 2–1 Suomen Cup win against SJK. Two weeks later, he scored a brace in a glorious 8–1 away win against SJK Akatemia for the Suomen Cup. On 4 March 2017, he scored a brace in a 6–1 home win against FC Jazz for the Suomen Cup. On 6 May 2017, he made his debut in the League with the club scoring in a 2–0 away win against EIF.
On 7 August 2017, Katidis left FF Jaro, signing a two-year contract with FK Olympia Prague of the Czech National Football League. On 12 August 2017, he made his debut with the club in a FNL 2-2 home draw against FK Viktoria Žižkov. On 27 August he netted the only goal in a 1–0 away win against Vlašim.
Katidis quickly became under 17, under 19 and then under 21 captain of Greece due to excellent performances while he was still playing for Aris FC. He was the captain of the under-19 team that lost in the final to Spain in the 2012 European Championship in Estonia. Scoring in a game on 16 March 2013, Katidis controversially celebrated the goal by giving the crowd a Roman salute. Katidis later apologized. The Hellenic Football Federation imposed a lifetime ban on Katidis, barring him from participating in all Greek national teams.
