Showdown mode has soo many issues, but so far so good. There are also some really unintuitive quirks with some badges.
Like to get "kill all" badge for the wedding level, you have to clean the map twice, as the level consist of two sequences and some enemies are exclusive to the first sequence only.
Actually, there might even be another extra kill one needs to do. I spend good few could hours trying to tick that one off the list.