Duet 16:15

אֱלֹהֶיךָ, בְּכֹל תְּבוּאָתְךָ וּבְכֹל מַעֲשֵׂה יָדֶיךָ, וְהָיִיתָ אַךְ שָׂמֵחַ שִׁבְעַת יָמִים, תָּחֹג לַיהוָה אֱלֹהֶיךָ, בַּמָּקוֹם, אֲשֶׁר-יִבְחַר יְהוָה: כִּי יְבָרֶכְךָ יְהוָה

For seven days celebrate the festival to the Lord your God at the place the Lord will choose. For the Lord your God will bless you in all your harvest and in all the work of your hands, and your joy will be complete. Duet 16:15

The word used in the Hebrew to describe "complete" at the end of the English translation is the word "Akh" which should be translated as "surly/very". The word Akh is used in different places with different meanings which is a very common element in Hebrew. Hebrew uses words in different ways due to the smaller number of actual words that it has, creating a multiple word meaning. In our case the word is used as a strengthening element that is telling use to be very joyful during the feasts. With all this said, the word "complete" does have a similar meaning in that that the text is telling use to be completely joyful without any sadness. The English transmits the idea while translating the word differently from its actual word meaning.