No major reason or animosity here
They just couldn't work together due to various script and schedule related reasons
Raghuvaran was supposed to work in Nayagan as Kamals son in law but injured himself causing Nassar to fly in on emergency
After that they just never got script or schedule compatibility
Raghuvaran evolved into a total villain / character artist by the late 1990s - due to his battle with addiction and Kamal had no suitable roles as he was primarily into comedies at that time
Raghuvarans wife Rohini was CLOSE TO KAMAL and even after his death, Kamal maintained ties with her.