People seemed to have missed that her name is Isca the Unbeaten, not Isca the Unbeatable. There's a difference. The fact that she hasn't lost up to this point in time ≠ it's impossible for her to be beaten. The 2007 New England Patriots were unbeaten until they weren't. Juggernaut is the Unstoppable Juggernaut, not the Unstopped Juggernaut. Unus is Untouchable, not Untouched, Blob is Immovable, not "the Unmoved," etc. But Isca's creator chose not to give her an "Un______able" epithet.
She was introduced all of three months ago, and people are talking about battleboard deathmatches against cosmic beings like Galactus. It's absurd. What we've seen to this point in time doesn't warrant that.