User: What are all Marvel movies with Thanos in it?
Assistant: Here is a list of Marvel Cinematic Universe films in which the character Thanos makes an appearance:
1. The Avengers (2012)
2. Guardians of the Galaxy (2014)
3. Avengers: Age of Ultron (2015)
4. Avengers: Infinity War (2018)
5. Avengers: Endgame (2019)