Rashi: They will appease him; they will be completely [at peace] with him.

R. Yonah #1: Anyone who has lovers below, it is known that he has lovers above. However, some have lovers below due to lack of proper Midos - if people of a city love the Chacham, it is because he does not rebuke them (Kesuvos 105b). Perhaps this verse is like we find about Avraham and Yitzchak - kings of Pelishtim came to make a Bris with them ¹ , for they saw that Hashem is with them.

R. Yonah #2: This is connected to verse 6. If one wants to repent from harming others via shaming, paining, pride and disgracing, there is no Kaparah via Chesed and Emes until he appeases his colleague (Yuma 85b). When Hashem is pleased with the way of his Teshuvah, he will put in their hearts to be appeased, and it is as if he never damaged.

Orchos Tzadikim (Sha'ar ha'Teshuvah DH v'Chen Amru, from Bereishis Rabah 54:1): Avraham's Yetzer ha'Ra made Shalom with him.

Orchos Tzadikim (Sha'ar ha'Ratzon): When a Tzadik is pleased with people, and people are pleased with him - anyone that people are pleased with him, Hashem is pleased with him (Avos 3:10).

Malbim: It already said "u'Rtzono Temimei Derech" (11:20) - there will not be external motives mixed in his Ru'ach. (He constantly seeks to follow the laws of Chachmah and Tzedek.) Then, Hashem makes his internal enemies - images of desire - at peace with him. Bad images will not come on his heart at all. This is Temimus! Via Shalom with internal enemies, Hashem will give to him Shalom also from external enemies, Midah k'Neged Midah. Just like he made enemies of the Divine Nefesh have Shalom with Hashem (Oyvav refers to Oyvei Hashem - images of the Yetzer), Hashem will make enemies of the body have Shalom with him.