Shouldn't you be comparing infinity war to the previous avengers movies?
A solo superhero movie isn't going to do better than Infinity war.
Domestically it is where Black Panther made 200 million + more than Age of Ultron and 50 million + more than first Avengers. It is Marvel's most successful film in the United States.
Internationally I don't think Black Panther has a prayer and could see Infinity War doing over a billion outside the US.
Black Panther - 675 million domestically, 640 million internationally
Infinity War prediction - 650 million domestically, 1.1 billion internationally