It's not exactly easy, but Metal Hero can just completely shred Barrier Girl. Even the slightest scratch destroys her barrier. They're both cool borgs, but I like Metal Hero better. I just wish I could use him at all.
"If less is more, just think how much more more will be!" - Dr. Frasier Crane http://www.backloggery.com/main.php?user=presea_hater
^I dunno, but I think it DOES deal more than a nuke and UC blast, considering how Metal Hero can one shot things nukes and Ultimate Cannons can't. The other borgs I'd be skeptical about are Garuda and the Machine Borgs, because they move too much to hit them dead on. I'll check that later when I have time.
On another note...I tried fighting with Metal today without his armor, good stuff lol. His vanilla combos actually do TONS of damage, which was suprising as he's armorless. The animation looks BA as well. Also, with your armor on, air dash cancelling by pressing A is really helpful, as it lets you dash and use the spin attack. Gotta get used to using him again, he's too fun.