Purpose of ができないと in this sentence "「まああたしも今、心身共に鍛え直している最中だからね、あれぐらいはできないと」"

Question

Context: Two girls are talking, one compliments the other about being able to kill a bear. The complimented one answers with:

"「まああたしも今、心身共に鍛え直している最中だからね、あれぐらいはできないと」"

Answer 1

There's a hidden incomplete expression to that,

あれぐらいはできないと（ダメですね）

meaning that it will be bad if the person was unable to do that much. It just expresses a possible causality (i.e. if you can't do it, something will happen).

In the same vein, think of it as like this:

ここまで運動したんだから、クマくらい倒せないとダメですよ。
After doing all that exercise, I'd die if I can't even beat a bear.

Or in a more practical situation,

宿題を今すぐやらないとお母さんに怒られますよ。
If you don't finish your homework now, mom will scold you.

P.S. I find the whole context and conversation amusing.