The question is about letting someone go and getting over it to remove the temptation of revenge.
There are many rituals you could employ, the symbology involved is to have something representing the person and their influence diminishing perhaps over time, or through the progress of the ritual, until they are removed completely from your sphere.
This could be a matter of burning a photograph and burying the ashes, or burying a personal item belonging to them. There are many different ways and I believe in the secrecy of occultism and so don't share my own spells.
Some other things you may want to take into account when creating the spell, the period of a waning moon is good, if you time it correctly and the ritual is drawn out I would personally have it finishing on the night of the new moon/dark moon. Saturday is ruled by Saturn which would be suitable for this type of work, you could also look up planetary hours if you wish.
Ultimately you must be ready to let go prior to the ritual, really ready. There must be no inclination to see that person again ever, if there is, you have inner work to do prior to outer work. A banishing spell is no good if any part of you intends to seek them out again and that part wins out.