"From childhood, he formed a friendship with King Duryodhana. This is because of the enmity he always bore towards you and natural destiny."

These are not my words but of Maharshi Narada to Yudhisthira.

Gandhari, being a mother of Duryodhana, said this to Dhritarashtra.
"He will be the destroyer of the lineage. O Lord! Do not listen to the views of these wicked ones who are nothing but children."

Pandavas had gone a long way towards Indraprastha but being summoned by Dhritrashtra for another Dyut, Yudhishthira accepted.

Though he knew that 'this would bring ruin'.

They were defeated again and they prepared for their exile.
When Duryodhana and Duhshasana mocked Bhima from behind, Bhima turned towards them and said:

"I will make you remember all this when I pierce your heart in battle."

"I will kill the sons of Dhritarashtra in battle, it is only after this that I will go to the abode of peace."

Never had Arjuna taken Karna this seriously.
But today he had committed a grave offence.
Karna had humiliated Panchali which Arjuna could never forget.

"I will kill in battle this jealous Karna.

"The mountains of Himavat might be removed from where they are, the maker of the day lose his brightness, the moon his coldness, but this vow of mine will ever be cherished."

and then the Pandavas along with Panchali went towards the forest leaving Kunti in Vidura's abode.

for the Pashupatastra tale follow this thread. https://twitter.com/PranjalUvaach/status/1253014665455702020?s=20