to be honest if he has admitted the mistake and that is somethign in itself i would give him the chance to fix the issue. if it doesnt work out how you want then he will have to pay for the laser removeal of the top half of that letter simple as. he will have insurance which will cover that kjind of expense and as he has already admitted fault i would give him the opportunity to fix it.

otherwise it looks bad on several fronts. if you go elsewhere they have a bad impression opf what might otherwise be a very good artist who had a lapse of concentration and while that is a very very bad trait in a tattooist it happens to us all from time to time.

give him the chance to fix it and make sure he knows if it is not done very well then you will be looking at having the top part of that letter corrected with laser treatment and you will want him to cover the cost. he will probably know someone who offers the treatment. many tatooists have laser removal tools as part of their kits now for coverups etc.

thats my 2c anyway