Whether or...not?

I'm writing one of my grad school admissions essays and stumbled on an issue: when, exactly, should 'whether' be used with 'or not'?

The sentence in question goes: (this is an essay on ethics)

I could not passively undermine the livelihoood of even one of my co-workers to satisfy a petty retaliation, regardless of whether John had truly been wronged.

or is it,

I could not passively undermine the livelihoood of even one of my co-workers to satisfy a petty retaliation, regardless of whether John had truly been wronged or not.

I'm stumped with this one....one moment the first option sounds best, then the second!

Cheers & thanks...