Garu kamma explanation garu-kamma (weighty karma) - if one has killed one's mother or father, for example. These types of karma outweigh any other possible result; one who has performed these at some time in this life cannot help but go to hell in their next existence.

This is a quote from Ven Yuttadhammos answer. 

My question is does garu kamma relate to murder of ones parents or could it also be a reason to shame them which drives them to suicide?
Decision to commit suicide is an individual decision. So it does not cause Garuka kamma for the one who does the shaming unless one had the intention to make them commit suicide.

There are also Garuka Kusala Karmas like Jhanas and Maggapala.