The word(s) "worthless" appears 19 time(s) in 19 verse(s) in Quran in Saheeh International translation.

(1) They ask you about the sacred month - about fighting therein. Say, "Fighting therein is great [sin], but averting [people] from the way of Allah and disbelief in Him and [preventing access to] al-Masjid al-Haram and the expulsion of its people therefrom are greater [evil] in the sight of Allah. And fitnah is greater than killing." And they will continue to fight you until they turn you back from your religion if they are able. And whoever of you reverts from his religion [to disbelief] and dies while he is a disbeliever - for those, their deeds have become worthless in this world and the Hereafter, and those are the companions of the Fire, they will abide therein eternally.

(2) They are the ones whose deeds have become worthless in this world and the Hereafter, and for them there will be no helpers.

(3) This day [all] good foods have been made lawful, and the food of those who were given the Scripture is lawful for you and your food is lawful for them. And [lawful in marriage are] chaste women from among the believers and chaste women from among those who were given the Scripture before you, when you have given them their due compensation, desiring chastity, not unlawful sexual intercourse or taking [secret] lovers. And whoever denies the faith - his work has become worthless, and he, in the Hereafter, will be among the losers.

(4) And those who believe will say, "Are these the ones who swore by Allah their strongest oaths that indeed they were with you?" Their deeds have become worthless, and they have become losers.

(5) That is the guidance of Allah by which He guides whomever He wills of His servants. But if they had associated others with Allah, then worthless for them would be whatever they were doing.

(6) Indeed, those [worshippers] - destroyed is that in which they are [engaged], and worthless is whatever they were doing."

(7) Those who denied Our signs and the meeting of the Hereafter - their deeds have become worthless. Are they recompensed except for what they used to do?

(8) It is not for the polytheists to maintain the mosques of Allah [while] witnessing against themselves with disbelief. [For] those, their deeds have become worthless, and in the Fire they will abide eternally.

(9) [You disbelievers are] like those before you; they were stronger than you in power and more abundant in wealth and children. They enjoyed their portion [of worldly enjoyment], and you have enjoyed your portion as those before you enjoyed their portion, and you have engaged [in vanities] like that in which they engaged. [It is] those whose deeds have become worthless in this world and in the Hereafter, and it is they who are the losers.

(10) And when they had thrown, Moses said, "What you have brought is [only] magic. Indeed, Allah will expose its worthlessness. Indeed, Allah does not amend the work of corrupters.