The story of this movie is the biggest weakness aspect of this movie, no clear motivation and no clear conflict.
It just feel like two strangers bump into each other for 5 sec and they fight. The motivation of the character is a Big no no, Batman fight Sup bc Sup one day may wipe the Earth, and Sup fight Bat bc Bat merciless kill criminal then later on that idea being tossed aside bc Lex told he to fight Bat. It may seem work on paper, but it doesn't then let to a big CGI fight.
And after all of this, In conclusion the fight of Bat and Sup made no sense.