Learn Farsi: اگر این موقعیت را بپذیری، ما رقیبی را شکست می‌دهیم. - If you accept this position, we will defeat a certain competitor.

This combination translates to "a certain competitor." Adding râ to a noun that already has the indefinite -i marks it as a specific, but unidentified direct object. The speaker has a specific competitor in mind, but is not naming them directly.

Why doesn't the other object, in moghe'iyat râ, also take an -i before the râ?

Because in (this) makes the noun strictly definite and identified. The speaker and listener both know exactly which position is being discussed. The -i plus râ pattern is only used when the object is specific but unidentified.

Why is the first verb bepaziri in the subjunctive mood?

Because it follows agar (if). In Farsi, "if" clauses that describe a possible future event use the subjunctive mood to show that the action is conditional and hasn't actually happened yet.

The English translation says "we will defeat," but isn't shekast midahim in the present tense?

Yes, it is the present indicative form of the compound verb shekast dâdan. In Farsi "if" sentences, it is very common to use the present tense for the result clause to talk about the near future, just as we often do in English.