2 Cor 1:11 wrote:συνυπουργούντων καὶ ὑμῶν ὑπὲρ ἡμῶν τῇ δεήσει, ἵνα ἐκ πολλῶν προσώπων τὸ εἰς ἡμᾶς χάρισμα διὰ πολλῶν εὐχαριστηθῇ ὑπὲρ ἡμῶν.
Murray Harris (NIGTC) suggests that διὰ πολλῶν needs to be taken as functioning within the subject NP τὸ εἰς ἡμᾶς χάρισμα.
Part of the awkwardness, arises from the fact that we would not passivized such a subject in English and that in fact, the abstract noun χάρισμα needs to be taken as a nominalized passive of χαρίζομαι as well. Make both of those active and it becomes much easier to read:
...so that many people might [active: given thanks]
for the gracious gift that many people gave on our behalf.
Perhaps its also really awkward in Greek. I'm not sure.