Since linquidation is to relieve the tension, would putting a ritardando be acceptable? It feels like cheating, so I was wondering if it was ok.
Yes, ritardandos are used all the time to relieve tension, but they can also be used to increase tension. A lot depends on circumstance within the piece, but a big aspect is what harmony you are slowing down on, or the goal of the rit.
If you slow down, and land on a V7, it will feel more tense. If you slow down and land on a I chord, it will relieve tension.
But they are always acceptable to use, it’s not cheating if the the outcome is what you want.