What if the superheroes charged with saving the world caused as much harm as good?

That conundrum — so much collateral damage — tears the Avengers apart in the unexpectedly dramatic “Captain America: Civil War,” one of the finest releases in the Marvel film catalog. The Cap and Iron Man find themselves leading from opposite sides as one backs government oversight of their well-intentioned escapades and the other champions autonomy. The heavy subject matter lends the proceedings a gravitas so often missing from the competing DC Comics film canon.

The Blu-ray (Disney, $25-$30), out Tuesday, adds an hour’s worth of bonus material, dominated by a two-part behind-the-scenes documentary. While there are a few deleted scenes, the main one is an extended funeral sequence, running about 6 minutes, that better defines the relationship between Steve Rogers and a side character.

Most engaging among the extras is the filmmakers’ commentary, which delves heavily into their use of plot misdirection -- everything is not what it seems at first -- and character motivation. Despite a lighthearted tone, it's a pithy affair that makes rewatching the blockbuster a pleasure.