Paedophiles.

Prisons are getting full, and (unfortunately) castration/death penalties aren't allowed.

Therefore, do you see any objection to a possible punishment for all convicted of this offence, whereby the offender is given a few permanent facial tattoos?

On the forehad: PAEDOPHILE

But they'll just wear a hat.

So on the left cheek: PAEDO
And the right: PHILE

And also on their back and chest maybe.

I don't see any argument against this. We aren't causing any direct pain or distress to them, so all the 'how DARE you even CONSIDER harming a child molestor!?' people wouldn't start crying.
Prisons wouldn't be full of them.
Re-offending rates would plummet. No-one would let such MONSTERS within a mile of their children.
It would ruin all hopes of employment, and furthering social circles, and would be a high deterrent.

?