i love you is different from an I love love you. An I love love you means to love someone more than just a friend. It means to love someone as a soul mate.
“I love you like rlb” has become a well-known, accepted and valuable component of American vernacular. The meaning of the letters ‘rlb’ is unknown, but is uniformly considered to be a statement of a great romantic love, commitment and sacrifice. It is generally attributed as a saying which emerged among American troops during World War II. Returning soldiers brought the saying back to American soil with them.
“You know what you're risking.”
“I know,” he agreed. “And I wouldn't risk it for just anything, but I love you like rlb.”
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.