19 Because in Him, it was well-pleased for all the fullness to dwell, 20 And through Him to reconcile completely all unto Himself, having made peace through the blood of His cross- through Him- whether the things upon the earth, whether the things in the heavens. Colossians 1:19 (Literal Emphasis Translation)
For in him, all the fullness of the Divine Nature dwells bodily. Colossians 2:9 (Catholic Public Domain Version)
In Colossians 2:9, it is clearly spelled out that the fullness dwelling within Jesus is namely the theotēs or divine nature bodily. In Colossians 1:19 it isn't so plainly specified what the fullness dwelling in Jesus through which all things were reconciled actually is and it's not so clear that we should necessarily substitute the fullness specified in Colossians 2:9 for the fullness in Colossians 1:19.
It's also interesting to note that, in Colossians 1:19, the two verbs are in the aorist tense indicating a completed act whereas the verb in Colossians 2:9 is in the present tense indicating an ongoing act.
For another (though not the only other) possible fullness candidate we have John 1:14-16:
14 And the Word became flesh and dwelt among us, and we have seen his glory, glory as of the only Son from the Father, full of grace and truth. 15 (John bore witness about him, and cried out, “This was he of whom I said, ‘He who comes after me ranks before me, because he was before me.’”) 16 For from his fullness we have all received, grace upon grace. -John 1:14-16