In reading through a volume of Luther's letters, one thing that comes out strikingly is the tenderness he was capable of. We know Luther the lion; we rarely hear of Luther the lamb. But it was there, as it should have been, since gentleness is not a spiritual gift and not an option depending on how we are wired but incumbent upon all believers (the fruit of the Spirit in Gal 5, not the spiritual gifts of 1 Cor 12, includes gentleness).
For example, in writing to Duke John Frederick in 1528, amid politically tumultuous times when war threatened, Luther writes:
God has promised great mercy to those who seek peace and endure guilt when he says: 'Blessed are the meek, for they shall inherit the earth.' War does not gain much, but loses much and risks everything. Gentleness, however, loses nothing, risks little, and gains everything.
A few months later Luther's one-year-old daughter Elizabeth died. He wrote to a friend:
My baby daughter, little Elizabeth, has passed away. It is amazing what a sick, almost woman-like heart she has left to me, so much has grief for her overcome me. Never before would I have believed that a father's heart could have such tender feelings for his child. Do pray to the Lord for me. In him, farewell.
--LW, 49:196, 203