The atrocity that specifically targeted Ukrainians from the list you provided is the Holodomor. The Holodomor was a man-made famine in Soviet Ukraine from 1932 to 1933 that resulted in the deaths of millions of Ukrainians.
While attacks on Cossacks and kulaks (wealthier peasants) can also be considered part of broader oppressive actions by the Soviet regime, the Holodomor is particularly recognized as a targeted atrocity against the Ukrainian population. Red Terror refers to the campaign of political repression during the Russian Civil War, affecting various groups throughout the Soviet Union, but it is not specifically aimed at Ukrainians.