1. EXID's Jeonghwa
EXID's Jeonghwa stated herself that she used to be a trainee at JYP. If she had stayed at JYP, there was a possibility she could have been scouted to be a member of TWICE rather than her current group, EXID! Because Jeonghwa was about 16 at debut, she would have been in the perfect age-range for JYP's TWICE and could have been a strong contender to be placed in that group over her current one!
2. Hyunseung (B2ST)
Hyunseung is one of the most well-known 'could have been' cases of any K-Pop group. If Hyunseung didn't join B2ST, he actually might have debuted as a member of K-Pop Kings, Big Bang! In fact, Hyunseung is still close to all the members of Big Bang and maintains that relationship today!
3. KARD's Somin
Though Somin of KARD debuted with the ensemble for the first time not long ago, KARD wasn't the group that Somin originally debuted in! In fact, Somin originally debuted onto the Korean music scene with girl group APRIL as a lead vocalist. Within a year's time, Somin had left APRIL and it can be speculated this was at the same time as her training for KARD began!
4. SPICA's Bohyung
Before Kim Bohyung joined SPICA, she originally was a YG trainee! In fact, Bohyung trained with 2NE1 for a little over two years. However, right before 2NE1's group debut, Yang Hyun Suk decided to debut 2NE1 with four members. Though there are no hurt feelings as Bohyung maintains a close relationship with the girls- especially Minzy!
5. BTS' Jin
BTS' Jin is known for striking visuals and his great vocal talents, however, he was originally street scouted for his visual appearances by an SM agent! Jin didn't go through with the SM agency, instead opting for Big Hit as his company of choice. However, odds are that if he were to have followed through with SM, he would have attained a position similar to that of EXO's Suho!
6. Gong Seung Yeon
Gong Seung Yeon, an actress who has been in a number of television series and variety shows, trained in SM for an extended period of time. Sung Yeon, who is actually the older sister to TWICE's Jeongyeon, spent a few years under SM and even managed to gain a spot on the shortlist to join f(x). After she lost interest in singing, she abandoned the opportunities to join f(x), as well as, Red Velvet. A strong visual, Sung Yeon would have made Red Velvet's visual department unstoppable!
Though HyunA's career was less of a 'could have been' case, she did originally debut with K-Pop group, Wonder Girls! Luckily for her, leaving was one of her best career moves. Not only was she able to dominate the music scene as a part of 4Minute, but she was also able to shine brightly as a solo artist. Leaving Wonder Girls was a blessing in disguise for HyunA!
8. NCT's Johnny
NCT's Johnny became an SM trainee at the age of 14 in 2008. Given the frame of his trainee time at SM, Johnny was a perfect contender to join the ranks of EXO. In fact, Johnny was even supposed to debut as a part of EXO. Johnny frequently trained with Chanyeol, but ended up joining NCT instead. Many netizens claim that NCT suits Johnny more than EXO would have and gives him more opportunity to shine.
9. EXO's Baekhyun and Chen
On that note, EXO's Baekhyun and Chen were both last minute additions to EXO. Because of their group timeline, it is a possibility that there could have existed an EXO sans two hugely talented main vocalists. If this were the case, it would have been extremely likely that the duo get assigned to NCT instead.
10. VIXX's Hongbin
VIXX's Hongbin is another would-have-been SM trainee! Hongbin, over the course of his trainee career, was contacted a multitude of times by SM agents pursuing a contract with him. Hongbin eventually chose Jellyfish Entertainment to join because his idol, Park Hyoshin, was there!