In addition to those I already mentioned (Ntouskos, Tentoglou, Tzengko), I'd like to add a few others for
Georgios Pilidis (wrestling) - He qualified for Tokyo which was impressive considering he's only 21. Since then he also won gold at the World U23 Championships (he had won a lot of medals at major events for his age group but this was his biggest achievement so far). 2021 was a great year for him despite having injury problems as well. Financially he lacks support so he is taking a break now to compete on Greece's Survivor (they offer big prize money plus it is a way to become famous and attract sponsors). I haven't watched any episodes yet (I think there were only one or two so far) but everyone is suddenly taking an interest in him and people who never heard of him are all saying he is the big favourite to win it all. I think it says a lot about how much he wants to make a big career in wrestling that he's willing to go to Survivor to acquire the money to support his career. He is clearly ambitious and has already done very well so I don't see why he can't achieve great things. I just hope competing on Survivor and missing a few months of training won't have such a negative impact on him (though his injury problems didn't stop him in 2021 either despite not being able to properly train at times).
Apostolos Papastamos (swimming) - He had some injury problems in 2021 also, so he didn't do well in Tokyo but I think he can do much better in 2024. Let's not forget he won gold in the 400 medley at the 2019 World Juniors and European Juniors, also won gold in the 200 medley at the European Juniors and bronze at the World Juniors. In the 400 medley he broke our NR in 2019 as an 18 year old and also broke the world junior record (I'm not sure if he still has it or not).
Anastasia Dragomirova (athletics - heptathlon) - Due to injury problems she was only competing in shot put in 2021, but she is planning to return to the heptathlon next year. She's never competed in a senior heptathlon yet, but some of her PBs are really impressive. 15.69 in shot put (this year, as an 18 year old), 45.76 javelin (last year, as a 17 year old), 1.78 high jump (last year, as a 17 year old), 6.44 long jump (in 2019, as a 16 year old). With those PBs, she would've been 1st in the shot put in Tokyo, 4th in the long jump and 10th in the javelin. She's still so young and can build on these, but her results in track events aren't that impressive although she hasn't competed a lot so it's tough to judge so far.