the one line in Avengers: Endgame that makes you feel real heartbreak because you know tony is gonna die later in the movie but he loves his daughter so much. The happiness you feel for Tony because he finally got the life he wanted but you feel pained because he sacrificed so much for it. The love you feel because Morgan Stark is so freaking cute. The sadness you feel for Morgan because little does she know that soon enough her father is about to sacrifice himself to save the rest of the world. My love for marvel.
This is used to tell someone you love them, often said to family. The first person to ever say these words was RDJ aka Iron Man/Tony Stark. And it made us cry very much... Instead of saying 'I love you!' in 2019 we say 'I love you 3000!'.
Tony's daughter claims she loves him 3000. It's an emotional line used in Endgame, Tony Stark says it back when he dies and creates a hologram of himself.