To what extent do means justify ends?

(Please read the phrasing carefully; yes, I meant to say it that way.)

To say “the ends [don’t] justify the means” suggests that there are some outcomes that might be desirable, yet have undesirable methods for being achieved.

Will desirable methods, “good” processes, acceptable means reliably lead to good outcomes? How can you be sure?

If they do not always lead to good outcomes, when do you begin to reassess the methods? And how do you begin to reassess them?

Can the means matter more than the ends?

I know the question is a bit abstract. If possible, it would probably be helpful to offer an example with your answer so the discussion can be a bit more concrete.