וְאַתֵּ֖נָה יְדַעְתֶּ֑ן כִּ֚י בְּכָל־כֹּחִ֔י עָבַ֖דְתִּי אֶת־אֲבִיכֶֽן׃
И вы знаете, что со всей моей силой я служил вашему отцу.
Ramban
THAT WITH ALL MY POWER I HAVE SERVED YOUR FATHER. That is, “from the outset, and he has been blessed since my coming.” It is possible that Laban’s flocks had been many, but that even the feebler ones were blessed since Jacob came, for Laban’s sons complained only out of jealousy of Jacob that he had gotten all this wealth.176Verse 1 here.
Radak
ואתנה..., I have served him faithfully whereas he related to me with deceit.
Radak
בכל כחי, as Yaakov tells Lavan to his face in verse 40 when he relates the harshness of the conditions he worked under.