i Register
In some senses, assuasive is marked as archaic. Watch for register when choosing this word.
adj
Mild, soothing.
If in the Breast tumultuous Joys arise, Musick her soft, assuasive Voice applies; Or when the Soul is press’d with Cares Exalts her in enlivening Airs.
“[…] Perhaps,” said Bounderby, starting with all his might at his so quiet and assuasive father-in-law, “you know where your daughter is at the present time?”
noun
Anything that soothes.
[…] the heat of the sun operates in all its vigour, without an assuasive to mitigate its force.
1817, Richard Yates, The Basis of National Welfare, London: F. C. and J. Rivington et al., § 9, p. 112, the bland, the courteous, the truly Christian assuasives of friendly attention