Mainly the claims that the CIA overthrew democratically elected leftist leaders in favor of more right-wing leaders.
I'm no historian, but as far as I know it isn't disputed that the CIA supported coups and attempted coups in countries such as Iran, Guatemala and Indonesia with the aim of installing leaders more closely aligned to US interests and opposed to socialism.
The answers in this thread describe CIA covert operations in numerous countries with the aim of securing more favourable governments. Due to the specific question being asked the answers from u/depressed333 and u/kostekbikernacki focus on more peaceful activities, but the fact remains that the CIA was actively meddling in the politics of foreign countries and wasn't averse to using violence to overthrow democratically-elected governments, as u/trackstarter describes.
For another talking point - CIA involvement in the illegal narcotics trade - see the answers in this thread:
Ed: I found some more answers about Guatemala and Iran by u/ColloquialAnachron and u/PotatoPactSignatory in this thread: https://www.reddit.com/r/AskHistorians/comments/elsxxn/its_the_mid1950s_and_im_a_reasonably_wellinformed/
And answers about Iran by u/Archiiii and u/kirkdict in this thread: https://www.reddit.com/r/AskHistorians/comments/chrold/the_cias_impact_on_the_events_of_1953_in_iran_was/