A partial answer.
Apart from eliminating main demon leaders, Devi also eliminated many ordinary demon soldiers, whose names were not given in Durga Saptasati aka Devi Mahatmya. Hence, providing complete list of demons eliminated by Devi, according to Devi Mahatmya, may not be possible.
The remaining questions are:
Why only Devi had to kill the demons?
Why not trimurthis not involved or supported?
Why demons agreed to battle with Stree murthi?
According to 2nd chapter of Devi Mahatmya, the energies of all Gods, including Shiva, Vishnu, Brahma, Indra, etc, came out of them, and got consolidated in the form of Devi.
तोऽतिकोपपूर्णस्य चक्रिणो वदनात्ततः। निश्चक्राम महत्तेजो ब्रह्मणः
अन्येषां चैव देवानां शक्रादीनां शरीरतः। निर्गतं सुमहत्तेजस्तच्चैक्यं
The issued forth a great light from the face of Vishnu who was full of
intense anger, and from that of Brahma and Siva too. From the bodies
of Indra and other devas also sprang forth a very great light. And
(all) this light united together.
All the Gods gave their respective weapons to Devi.
शूलं शूलाद्विनिष्कृष्य ददौ तस्यै पिनाकधृक्। चक्रं च दत्तवान् कृष्णः
शङ्खं च वरुणः शक्तिं ददौ तस्यै हुताशनः। मारुतो दत्तवांश्चापं
The bearer of Pinaka (Siva) drawing forth a trident from his own
trident presented it to her; and Vishnu bringing forth a discus out of
his own discus gave her. Varuna gave her a conch, Agni a spear; and
Maruta gave a bow as well as two quivers full of arrows.
After the elimination of Mahishasura by Devi, the devas said:
भगवत्या कृतं सर्वं न किंचिदवशिष्यते॥३४॥
यदयं निहतः शत्रुरस्माकं महिषासुरः। यदि चापि वरो देयस्त्वयास्माकं
संस्मृता संस्मृता त्वं नो हिंसेथाः परमापदः। यश्च मर्त्यः
‘Since our enemy, this Mahishasura, has been slain by Bhagavati (i.e
you) everything has been accomplished, and nothing remains to be done.
And if a boon is to be granted to us by you, O Maheshvari, whenever we
think of you again, destroy our direct calamities.
And, Devi agreed to this wish.
When Shumba and Nishumba defeated Devas, the latter prayed to Devi. Devi took the of beautiful form. Knowing the beauty of Devi, Shumba and Nishumba sent messengers to Devi for choose them as her partner.
Then Devi says that since she took an oath of choosing a partner, who defeats her, Shumba and Nishumba had to fight with her.
किं त्वत्र यत्प्रतिज्ञातं मिथ्या तत्क्रियते कथम्।
श्रूयतामल्पबुद्धित्वात्प्रतिज्ञा या कृता पुरा॥११९॥
यो मां जयति संग्रामे यो मे दर्पं व्यपोहति। यो मे प्रतिबलो लोके स मे
Hear what promise I had made already out of foolishness. “He who
conquers me in battle, removes my pride and is my match in strength in
the world shall be my husband.”
That was how the demons were dragged into the battlefield by Devi.
The main demons that were killed by Devi were:
Mahishasura, Dhumralochana, Chanda, Munda, Raktabija, Nishumba and Shumba.