It isn't slugs. The young leaves would be targeted before older peppers. If the inside of the cavity near the seeds are black and rotting I have a couple of suspects
Usually pepper weevils come out of the ground around now. They lay an egg on the pepper flower and the larvae burrows into the pepper eating the insides as the pepper grows. You will notice the infesting peppers look like they are ripening faster even showing some yellow streaks, then they get water logged and mushy. If you examine the cap of the pepper you will find a small hole at the edge of the cap where the weevil emerged. They mate and then hibernate in the ground until next year. To avoid them, you have to rotate the peppers to another part of the garden. Adults feast on leaves and fruit of nightshades.
European corn borer also causes that kind of damage. It is the larvae of a moth that likes to burrow into corn ears but also peppers and feed on turf roots. I don't think this is what is bothering your plant.
https://www.pubs.ext.vt.edu/content/dam ... 06_pdf.pdf
Here are some other common pests of peppers
https://www.ipm.uconn.edu/documents/raw2 ... ation2.pdf
That bug on your leaf is also suspect. I can't tell what it is, but it is probably not a good bug.