Superman (although widely referred as Superman 64) is a Nintendo 64 video game released in 1999, based on Superman: The Animated Series. It is infamous for its perceived extreme lack of quality, clunky graphics, irresponsive controls, very repetitive gameplay (many "fly through rings" portions), confusing layout and mediocre rendering, among others.
It was developed by the French studio Titus. The head developer later revealed in an interview that the game was developed into something different, but the DC comics executives forced the developers to make many changes, which, combined with the short time left to work on, inevitably led into the product that came to be.
One beta rom was revealed, but it is unknown if more developed content is unrevealed. However, it is extremely unlikely that any of this content will be revealed because according to a interview with Eric Caen, co-founder of the company, by YouTube user Proton Jon, he reveals that he is not allowed to detail what was removed. Potentially meaning that a Non-Disclosure Agreement is still on the game.
Here's a link to the interview: An Interview With Eric Caen