If we look into Bhramanda Purana the Intergalactic War between Sri Lalitha Maha Tripura Sundari and Bhandasura is unparalleled.
Please see the list of Astharas which Bhandasura used and the counterpart Amma used that Nullified them :
Andhathamishra - Surya Aasthra
Mooka Ashtra - Gayatri Manthra
Sarva Roga Ashtra - Nama Thraya Asthra (Achutha Anantha Govinda)
Asura Asthra (All the Asuras were Born - Mahishasura, Rakthabeeja, Shumbha, Nishumbha etc) - Amma Used Durga Asthra
Amma cleared the Entire Warrior Sena with one Asthra Maha Pashupatham and finally Amma killed Bhandasura and burned down his Sunyaka Nagaram by Kameshwara Asthra.
So ashtras are Manthra and Devatha Shakti that generate Power in various ways.
Even the Indra's Vajram, Yama Dandam, Vishnu Sudarshana, Shiva Trishulam etc etc all are Ashtras which have a Manthra and Devatha which can be worshiped by anyone.
Personally when read Mahabharatha - felt like Pashupatha Ashtra was very special and furious in Nature.
After getting the Pashupatha Asthra from Shiva, Indra invited Arjuna to Heaven (Swarga Lokam). After spending some time there Indra informed Arjuna that there is a Clan of Asuras named Nivatha Kavachas who are bothering him and his Kingdom. So asked Arjuna if he could fight them and get rid of them. Arjuna happily aggred to the offer and wore a Devine Armour given by Indra and on the Chariot with Green Horses and a charioteer named Mathali carrying his Bow Gandeevam Arjuna went to the war and won all the 30 Million Rakshasha single handedly.
While returning back to Amravati (Heaven's Capital) he saw a place and asked what is this place to Mathali. He said they are another set of Asuras or Rakshasha that occationally bother Indra and other Devathas. Hearing Arjuna said let's take care of them too. In headcount they are 60000 people called as Kalakeyas but 10 times more dangerous than Nivatha Kavachas.
So Arjuna invited them for a Mortal Combat. In which after a furious war. The Kalakeyas started to Attack Arjuna all at once. First Time then Arjuna used the Devine Weapon given by Shiva - The Pashupatha Asthra.
The moment he used it the weapon got divided into Million Arrows and from each arrow it created other weapons like Khadgam, Thomaram, Shulam, Chakram, Gadha etc etc and also from it emerged different wild Animals, Rakshasha, Asura, Bhootha, Preetha etc etc and killed all the 60000 Kalakeyas at once and disappeared back as if nothing happened.
The special part of Arjuna is that he did not use this Ashtra in the 18 days of Kurukshetra War.
From this glorious incident from Mahabharatham - Aranya Parvam we personally have a Favouritism for the Shiva's Pashupatha Asthra.
There other major Asthras too like Naraya Asthra, Bhrama Asthra, Varuna Asthra, Agneya Asthra, Vayuya Asthra, Naga Asthra, Garuda Asthra, Samohana Asthra, Anjalika Asthra etc etc.
Hope we have presented it properly
Hara Hara Maha Deva