The phrase "Lord, have mercy upon us" is a common plea for forgiveness and compassion from a higher power. There are several synonyms that can be used to express this sentiment, including "God, be merciful to us", "Lord, show us grace", "Have pity on us, Lord", and "Grant us your compassion, O God". Other variations include "God, have mercy on us sinners", "Lord, forgive us our trespasses", and "Have mercy on us, O Christ". Each of these phrases conveys a deep sense of humility and recognition of human fallibility, and can be used in a variety of religious or spiritual contexts.