Kulak isn't a ethnic group, so there can't be a "genocide of the Kulaks". The definition of Kulak were the landowners who wouldn't collectivize. And yeah, a bunch of them were executed doing shit like lighting grain on fire during a famine out of spite for the government.
Alright, what is the word for systematically killing a large group of people grouped by something other than ethnicity?
Death penalty? At least that's what they call it in the USA.
Or, for doing absolutely nothing. It didn't even matter if they actually were "rich" or not.