John Gill Commentary Jeremiah 32:18

"who showest lovingkindness unto thousands, and recompensest the iniquity of the fathers into the bosom of their children after them; the great, the mighty God, Jehovah of hosts is his name;" — Jeremiah 32:18 (ASV)

You show lovingkindness to thousands
Not to thousands of persons only, but to a thousand generations, even such that love, fear, and serve him; see (Exodus 20:6) (Psalms 105:8) ; this is very properly added, for the further strengthening of faith; for though the omnipotence of God assures us that there is nothing but what he can do, yet it gives us no certain encouragement he will do this, or that, or the other, in a favourable and gracious manner; but this his loving kindness, experienced by a multitude of persons in all ages, gives reason to hope for.

and recompenses the iniquities of the fathers into the bosom of their
children after them ;
it is added in the decalogue, from where these words are taken, "of them that hate me", (Exodus 20:5) ; and here the Targum adds, ``when they go on to sin after them;'' when they imitate their fathers in their wickedness, and commit the same sins they have done, and continue in them; wherefore, having filled up the measure of their fathers' sins, they receive a just and full recompense of them into their bosom; which denotes both the certainty of it and the fullness of it: the prophet formed in his mind just notions and ideas of the divine Being, as being not only gracious and merciful, but holy, just, and righteous; and it may be he strikes at the Jews, who might complain of God, as they sometimes did, for being punished for their fathers' sins, as if they themselves were innocent and guiltless.

the Great, the Mighty God, the Lord of hosts [is] his name :
"great" in all the perfections of his nature, and greatly to be praised, loved, and feared; "mighty" to do whatsoever he pleases; and who, agreeably to his name, has all the hosts and armies of heaven and earth at his command; and what is it that he cannot do?