Warrior Priests and the unit they are with hate all models in any of the following armies: all Chaos (Chaos Warriors, Beastmen, Daemons and Chaos Dwarfs), all Undead (Khemri and Vampire Counts), all Skaven.
Note that this power does not affect other characters (they are more difficult to influence than the average soldier) and units Immune to Psychology are not affected by this power as well. Also note that Warrior Priests will never join units of warriors who are not devout to Sigmar, so they cannot join units of Knights of the White Wolf.