Toaru Majutsu no Index SS: Kanzaki - Chapter 7: The Destination of Salvation. GUNGNIR.

This novel is also known as The Demons Beside Me

Chen Zhao can summon demons and see Death.

“Beelzebub, use your Gluttony ability to treat this patient’s anorexia.”

“Raymond, this old man wants to regain his manly function. You know what I mean.”

- Description from Novelupdates

“If you had E-class or F-class skills, history would have changed.”

Jung-woo Jung, a hero who has everything except ability.

Then the world gave him unlimited power.

He went from an ordinary student to a god-level master in manufacturing.
Continuously progressing, processing range from hundreds of meters to tens of atoms, processing precision from microns to nanometers to atoms and molecules, everything was possible.
Wassenaar Accord? The embargo against China? What we have banned are technologies that China doesn’t care much about. Most of the member states have to import technology from China, shouldn’t the member states have a meeting to discuss and bring in China as well?
Forbidden chip sales? Is there a mistake? We barely managed to maintain our low-end market with a large amount of subsidies, it’s already good enough that China didn’t initiate an anti-dumping investigation. President, are you sick?
Hmm, it seems like living cells can be processed precisely as well. Do you need to refine the cancer cells that you are spreading out?

- Description from Novelupdates

You thought being reincarnated as an extra-side character was bad? Imagine being thrown into the body of a villain who is disowned by his own family and discarded by the author.