けでな

[mella]

強くなれ、命がけでな。
what about your life, if you don't become stronger?
I don't know how to translate けでな.

[becki_kanou]

As someone else suggested, you seem to be having a lot of parsing errors. This is not けでな but 命がけ・で・な

命がけ means risking one's life. 強くなれ is a command. Get stronger! (by risking your life). It's an odd sentence and hard to tell the nuance without more context...

[Hyperworm]

When dictionaries aren't turning anything up, it's worth trying a few other possibilities for how a sentence could be broken up. Try to overcome the parsing errors ^^;

A bit of further detail on 命がけ.

Despite its definition as "risking one's life", and Kenkyusha's entry

命がけで‥‥する
risk one's 「life [neck] 《for...》; stake one's life 《on...》 by doing...; do ... at the risk of one's life

which also implies very literally risking your life,
I think 命がけ also has some similarities to "as though your life depended on it" / "with every last bit of effort you can muster".

At the very bottom of Kenkyusha's entry it provides support for this via this example sentence:

彼は何でも思いこんだら命がけというタイプだ.
He's the type of person who, once he makes up his mind on something, puts everything he has into it.

Hopefully this makes the sentence a little less confusing.