私がそれを信用していたら、最後は私が負けていただろう。

English Translation

I trust that, in the long run, I will not be a loser.

Is this right?

Because if I try to translate it literally, it kind of mean the opposite:

If I had faith in that, the conclusion is, I would probably be defeated.

So, making it a bit more natural sentence: If I trusted that, in the end, I would have lost.

Yes, it seems wrong.

It looks like the author parsed it as:
(If I trust THAT,) (then, at then end, I will have lost).

I’m not a native speaker, and my Japanese studies were too long ago to present a correct sentence now, but for the meaning to match, the sentence structure and order would have to be something like this:

(In the long run) (I will not be a loser) (I trust).

This is what Google Translate suggests:
長期的には、私は敗者にならないだろうと信じています。

It looks much better, even though it translated the “loser” literally, as a noun, while I suspect a Japanese would use a verb there,