I’m making this list to show what is evident and is artists don’t will always release a hit song and that’s ok lol. Stans will scream “flop” just because a song wasn’t as big as the previous one.
This is base on korean chart performance also if underperformed base on overall standards not the artist one.
2018: DDU-DU DDU-DU (HIT)
2019: Kill this love (Underperformed)
2018: RBB (Underperfomed)
2019: Zimzalabim and Umpah Umpah (Underperformed)
2019: Psycho (HIT)
2020: Black Swan (Underperformed)
2020: Dynamite (HIT)
4. TWICE
2019: FANCY (HIT)
2019: Feel Special (Underperformed)
2018: Love Scenario (HIT)
2018: Killing Me (Underperformed)
6. MOMOLAND
2018: BBOOM BBOOM (HIT)
2018: BAAM (Underperformed)
2019: I’m so Hot (Underperformed)
7. Aespa
2020: Black Mamba (Underperformed)
2021: Next Level (Hit)
8. EXO
2017: Ko Ko Bop (HIT)
2018: Tempo (Underperformed)
The list can go on and with more songs added even for the groups I mentioned. If you have examples feel free to add it.