What weapon did Arjuna used to kill Karna?

In some stories, it is also said that Lakshmana- brother of Lord Rama used same Anjalikastra to kill Indrajit. This astra came into prominence when Mahabharat’s hero Arjuna used it to kill Karna.

How did Karna get Pashupatastra?

Timeline also negates the false belief that Karna got Mahapasupata from Parashurama,who never got it at all. Karna got astras from Parashurama much before Arjuna pleased Sadashiv with his penance and valour. It was always about Brahmastra that Karna was denied by Drona but got from Parashurama.

Why did Arjuna not use Pashupatastra against Karna in the Mahabharata?

Raudrastra is not another name of Pashupatastra i will explain the difference between both weapons. Because Arjuna never needed to use it against Karna. Arjuna would not have needed the Pashupatastra to face Karna. Because Arjuna never used it on Karna.

What is the mantra to obtain the weapon of Pashupatastra?

The mantra to obtain the weapon is sealed by Lord Shiva so that it cannot be misused under any circumstances, especially in the Kali Yuga. The pashupatastra can be neutralized only through another pashupatasra or any other astra (weapon) whose presiding deity is Lord Vishnu.

Is the raudrastra of Arjuna good enough?

Raudrastra is lower level weapon of shiva but good enough to destroy entire city of celestial demons. Arjuna also did not use mace of Lord Yama himself who was god of death and has given one version of his mace to him. He also did not use noose of Varuna which could tie anyone or weapons of kubera.

How good was Arjuna at firing Divya Astras?

Firing divya astras required great skill and strength very few warriors could do it efficiently.Arjuna was not very good at it . He also couldn’t wield his gandiva properly . whereas karna , bhishma and drona were much more powerful and skilled than arjuna in firing divya astras.