According to Jainism:

1. Yes, at present Krishna is believed to be in “hell” (Naraka)

- In Jain universal history, Krishna is the 9th Vāsudeva (a powerful world‑conqueror type hero). - Because of very heavy hiṁsā (violence) – especially the Mahābhārata war and many killings done under his leadership – his soul accumulates intense pāpa karma. - As a result, after death he is reborn in a Naraka gati (hellish state). - Some Jain texts specify the 3rd hell (Vālukaprabha) as his current state, from where he will eventually come out when that karma is exhausted.

1. Hell in Jainism is not eternal

- No one stays in Naraka forever. - When the specific karmas causing that hellish birth are finished, the soul leaves Naraka and takes another birth according to remaining karmas.

1. Future: Krishna will become a Tirthankara and attain moksha

- Jain scriptures also say that in a future time‑cycle, after completing his Naraka life and further births, Krishna’s soul will be born as a Tīrthankar named “Amam (Amama) Svāmī” (usually listed as the 12th Tirthankara of a future set). - At that time he will attain keval‑jñāna (omniscience) and finally moksha (liberation).

1. How Jains view Krishna overall

- So, in Jainism Krishna is neither a permanent “God” nor eternally damned. - He is seen as: - a great but karmically burdened hero (Vāsudeva), - presently experiencing the result of his violent karmas in Naraka, - and destined in the distant future to become a liberated Tirthankara.

You can read a simple explanation about this topic here