This chapter of Mahabharata mentions that Durga killed Kaitabha.
I bow to thee that art fond of battle! O Uma, Sakambhari, O thou that art white in hue, O thou that art black in hue, O thou that hast slain the Asura Kaitabha, O thou that art yellow-eyed, O thou that art diverse-eyed, O thou of eyes that have the colour of smoke, I bow to thee.
But, actually Vishnu slayed both Madhu and Kaitabha. So my question is, did Devi kill Kaitabha?
From Markandeya Purana (Saptashati 1st Chapter). Lord Vishnu kills Madhu Kaitabha as:
तथेत्युक्त्वा भगवता शङ्खचक्रगदाभृता।
कृत्वा चक्रेण वै च्छिन्ने जघने शिरसी तयोः॥103॥
Saying 'Be it so', Bhagavan (Vishnu), the great wielder of conch, discus and mace, took them on His loins and there severed their heads with His discus.
Just prior to this, Adi Shakti deludes in such a way that they tell them to ask for a boon for Lord Vishnu.
तावप्यतिबलोन्मत्तौ महामायाविमोहितौ॥94॥
उक्तवन्तौ वरोऽस्मत्तो व्रियतामिति केशवम्॥95॥
And they, frenzied with their exceeding power, and deluded by Mahamaya, exclaimed to Vishnu, 'Ask a boon from us.'
Prior to this event, there is a prayer by Lord Brahma to Mahamaya, and at last he asks for:
मोहयैतौ दुराधर्षावसुरौ मधुकैटभौ।
प्रबोधं च जगत्स्वामी नीयतामच्युतो लघु॥86॥
बोधश्च क्रियतामस्य हन्तुमेतौ महासुरौ॥87॥
O Devi, Delude these two unassailable asuras Madhu and Kaitabha with your superior powers. Let Vishnu, the Master of the world, be quickly awakened from sleep and rouse up his nature to slay these two great asuras.'
So, the chain of the events described in Saptashati is as; Madhu and Kaitabha arise from Karnamala (ear wax) of Lord Vishnu and start tormenting Lord Brahma. But Lord Vishnu was sleeping at that time, so Lord Brahma prayed to Mahamaya Devi to wake up Lord Vishnu and delude Madhu Kaitabha. Mahamaya then wakes up Lord Vishnu from his sleep and during the fight also deludes Madhu Kaitabha. So, though Madhu Kaitabha ended at the hands of Lord Vishnu, Mahamaya also ended them by waking up Lord Vishnu and deluding Madhu-Kaitabha. So, Devi is also praised by names like 'MadhuKaitabha Samhantri' (Destroyer of Madhu and Kaitabha).
Devi Bhagavatam says Vishnu, aided by the Goddess, killed them:
https://www.wisdomlib.org/hinduism/book/devi-bhagavata-purana/d/doc57108.html
Hearing their words, Janārdan Visnu addressed them as follows:-- “O two Dānavas, mad for war! Come and fight with me as you like; I will surely curb your pride. O two powerful ones! If you trust me, come and fight”. Hearing this, the two Dānavas in the midst of that mass of water resting without any support, came up there to fight, with their eyes rolling with anger. The Daitya, named Madhu, became very angry, came up quickly to fight while Kaiṭabha remained where he stood. Then the hand-to-hand fight ensued between the two mad athletes; Bhagavān Hari and Madhu became tired; Kaiṭabha came up and began to fight. After that Madhu and Kaiṭabha joined and, blind with rage, began to fight again and again hand to hand with the very powerful Viṣṇu. And Bhagavān Brahmā and the Prime Force Ādyā Śakti witnessed this from the celestial Heavens. So the fight lasted for a long, long, time; yet the two Dānavas did not feel a bit tired: rather Bhagavān Viṣṇu became tired. Thus five thousand years passed away; Hari then began to ponder over their mode of death.
He thought :-- “I fought for five thousands of years but the two formidable Dānavas have not been tired anything, rather I am tired; it is a matter of great surprise. Where has gone my prowess? and what for the two Dānavas were not tired; What is the cause? This is a matter, now, seriously to be thought over”.
Now the four-armed Vāsudeva, seeing them at a sufficient distance, began to ponder in his mind thus :-- “How their death can be effected? Thinking for a time, he came to know that they have been granted, by the Supreme Śakti Devī, death at their will (Iccāmrityu); and therefore they are not getting tired. I fought so long with them uselessly; my labour went in vain. How then can I now fight, with this certain knowledge. Again if I do not fight, how these two Dānavas, elated with their boon and giving troubles to all, be destroyed? When the boon is granted by the Devī their death is also well nigh impracticable. Who wants his own death, even placed in very great distressed circumstances. Attacked by terrible diseases, reduced to indigent poverty no one wants to die; so how can it be expected that these two haughty Dānavas would want their death themselves? Therefore it is advisable me to take refuge of that Ādyā Śakti, the giver of the fruits of all desires. No desires can ever be fructified unless She is thoroughly pleased. Thus thinking, Bhagavān Viṣṇu saw the beautiful Devī Yoga Nidra Śiva, shining in the air. Then the supreme Yogi, Bhagavān Viṣṇu, of immeasurable spirit began to praise with folded palms that great Bhuvaneśvarī Mahā Kāli, the giver of boons for the destruction of the Dānavas. “O Devī! I bow down to Thee O Mahāmāyā, the Creatrix and Destructrix! Thou beginningless and deathless! O auspicious Chandike! The Bestower of enjoyment and liberation I do not know Thy Saguṇa or Nirguṇa forms; how then can I know Thy glorious deeds, innumerable as they are. To-day Thy undescribable prowess has been experienced by me, I being made senseless and unconscious by Thy power of sleep. Being tried again and again by Brahmā with great care to bring me back to my consciousness, I could not become conscious, so much my senses were contracted down. O Mother! By Thy power, Thou didst keep me unconscious and Thou again hast freed me from sleep, and I also fought so many times. O giver of one’s honour! Now I am tired; but Thou hast granted boon to the two Dānavas and therefore they are not getting tired. These two Dānavas, puffed up with pride, were ready to kill Brahmā; and therefore I challenged them to fight with me and they too are fighting fiercely with me in this vast ocean. But Thou hast granted them the wonderful boon that they will die whenever they will; and therefore I have now come to Thy refuge, as Thou protectest those that come under Thy shelter. Therefore, O Mother, the remover of the Devaś troubles! These two Dānavas are become exceedingly elated by Thy boon and I, too, am tired. Therefore dost Thou help me now. See! those two sinners are ready to kill me; without Thy grace, what can I do now? and where to go?”
50-59. Thus praised by the eternal Vāsudeva Jagannātha Hari, with humility and pranams, the Devī Mahā Kāli, resting in the air, said smiling :-- “O Deva deva Hari! Fight again; O Viṣṇu! These two heroes, when deluded by My Māyā, would be slain by you; I will delude them certainly, by My side long glance; O Nārāyana! then slay quickly the two Dānavas, when conjured by My māyā”.
