Similar word to unthriftiness:

decay, desolation, destruction, devastation, dilapidation, dissipation, disuse, exhaustion, expenditure, extravagance, fritter, havoc, improvidence, lavishness, loss, lost opportunity, misapplication, misuse, overdoing, prodigality, ravage, ruin, squander, squandering, unthriftiness, wastage, wastefulness