In "Encounter at Farpoint", Q puts Picard and the Enterprise crew on trial, arguing that humanity is a dangerous race and should be destroyed. When they later save the life of a kidnapped alien, Q agrees to defer judgement, though he suggest this won't be his last word on the matter.
William Shatner's well-documented feud with former co-star George Takei simmered for decades. Both actors took jabs at each other during major media interviews, including on Howard Stern, Real Time with Bill Maher, and even in their autobiographies.
Lore is an android of the same model and appearance as Lt. Commander Data of the U.S.S. Enterprise-D. Both were created by Dr. Noonien Soong, but Lore was equipped with an emotion chip that made him unstable. He was responsible for the death of all colonists on Omicron Theta and proved exceptionally dangerous during several encounters with his "brother" Data and the crew of the Enterprise.