I've been wanting to try and make a costume like this for awhile now, so I went ahead and gave it a go.
It's Zero from the Megaman X series! Specifically, Megaman X4-X6.
Here's a video of me going through the SMBX 2.0 Mario Challenge as Zero:
You can download the costume here: https://drive.google.com/open?id=1QXW6D ... xzWgv5EZMu
You can get more info about the SMBX 2.0 Beta 3 here: viewtopic.php?f=69&t=16814
It's my first actual costume for a character, and as such I'm sure it's not perfect, but I thought I'd give the whole costume-making thing a shot. I was even able to include some SFX too! Namely, the SFX for when he takes damage and loses a life. I know that the 2.0 characters will be reworked, but I had already gotten close to finishing by the time I found out (and really wanted to finish), so I just finished it. I'm probably going to have to update things anyway because of the reworking, so I could really use some feedback on the costume so that I can improve it when I do!
One thing I'm already aware of is that the Zero costume currently isn't quite as tall as Uncle Broadsword. I'm trying to figure out how to fix that and keep his frames within 100x100 pixels while still being this style and not distorted. I'm also aware that nothing in SMBX is X4-X6 styled, so he doesn't generally "fit in," but this costume wasn't really meant to anyway.

Here's how add it to 2.0 if you haven't added costumes before. If anything's incorrect, please correct me: