IMFACT - due to a mistranslation on an article on the main page of AKP, a translator announced their disbandment. Even after the leader of the group commented and said they haven't disbanded, they just all left their company and will make music together in the future when opportunities allow them, a lot of people still think they've disbanded.
Weki Meki - a lot of post Produce 101 season 1 groups have disbanded and this one has been inactive for a long time.
ZE:A - also mistakenly reported to have disbanded but all of the members assured fans that they'll meet as a group again in the future. Have been on a hiatus for 5 years.
VIXX - most members left the company, but the group still exists and they want to come back together.
Can you think of anyone else?