Henry Cavill originally teased the black Superman suit for Justice League before director Zack Snyder left the movie when his daughter took her own life, in that time WB took over control and replaced Snyder with The Avengers director and changed the entire movie -- including the entire plot of the black Superman suit.
Back in July 2017, I wrote about the black Superman suit and said at the time: "Could he return with the black Superman suit that Henry Cavill teased on Instagram earlier this year? Superman could even rock a beard, which would be beyond awesome. A bearded, evil Superman?"
I continued, pondering: "That sounds like Superman being evil to me... so bearded Supes with a black suit? PLEASE, DC... but I have one request: bad Superman is beaten by Justice League, for the true Superman to arrive after. I want the true hero behind Superman to be in Justice League, but I'm totally down with a pissed off, and vengeful Kal-El".
It seems, I was pretty much spot on -- Superman was evil, and chose the black suit (that he walks past in the deleted scene I have embedded above). Snyder himself unveiled a bunch of details on his cut of Justice League, saying he originally planned 3 movies in the Justice League franchise (we knew this) -- but there's some new info, too.
Snyder himself confirmed he shot Henry Cavill in the Superman suit that we've seen in black, where as later in the movies (in Justice League 2 which would've been released in 2021 and continued the story Snyder was telling) Superman would've returned with the iconic suit.
Justice League was also originally meant to be four hours long, Snyder himself confirming the news and saying to not push him to reveal more (because we know he will) about Green Lantern. Yes... Green Lantern was in Justice League. I'll leave you with that thought.