穏健【おんけん】
quiet, dependable, uniform, (politically) moderate
穏やか【おだやか】
calm, quiet, gentle, peaceful, mild, moderate, reasonable, amicable
平穏【へいおん】
tranquil, calm, restful, peaceful, quiet
穏便【おんびん】
gentle, peaceable, amicable, quiet, without fuss, simply
穏当【おんとう】
proper, reasonable, right, appropriate