"Who knoweth if He will return and repent. . . turn unto the Lord your God:  for  he  is  gracious  and merciful, slow to anger, and of great kindness, and repenteth Him of the evil" (Joel 2:14,13). These are the attributes of 'the Lord' that passed before Moses in Ex. 34:5,6, thus also indicating that this was an Angel. Jonah 4:2 makes the same connection.

2:25 see on 1 Kings 22:22

As Israel’s enemies make themselves strong, so the weak shall become “strong”- gibbor (Joel 3:10). I take this as a reference to the repentant and feeble remnant of Israel becoming strong, rather than [as it is often read] weak Gentile nations becoming strong in the last days. Thus there will be a standoff between the ‘mighty men’ of the Gentiles (Joel 3:9) and the ‘mighty ones’ of God, the Angelic hosts working through the feeble remnant on earth whom they will make into ‘mighty ones’. Hence the many references in the prophets to the ‘mighty men’, the gibborim of the Gentiles, being slain in the last day. It will be the final showdown, screened world-wide, between the hosts of God and those of men- although we live it all out, we see it all, in our daily experience now.

"Thither cause Thy mighty ones (cp. 'Elohim') to come down" (Joel 3:11) speaks of God manifestation through Angels to destroy the latter day invader, the latter-day Sennacherib.