In Jain Dharma, a long stay in Narak is generally caused by very intense paap karmas and especially by actions done with strong cruelty, hatred, violence, and selfishness.

Some main causes are:

• Himsa: causing severe injury or death to living beings, especially with cruel intent
• Extreme anger, revenge, and hatred
• Deceit and fraud done to harm others
• Stealing and exploitation of others with harshness
• Falsehood that causes great suffering
• Very strong greed, attachment, and possessiveness
• Violence against vulnerable beings such as helpless animals or beings with weak protection
• Delighting in cruelty or encouraging others to harm living beings

In Jain teaching, the more intense, repeated, and heartless the sinful action, the heavier the karmic bondage and the longer the suffering in Narak.

The deepest cause is not only the outer action, but the inner state of the soul:

• cruelty
• passion
• wrong belief
• lack of compassion
• disregard for ahimsa

The way to avoid such bondage is:

• practice ahimsa
• control anger, greed, pride, and deceit
• live with compassion
• follow right faith, right knowledge, and right conduct

If you want, I can also explain this according to Jain karma theory in a very simple way.