What is ironic about the things Iago says to desdemona

Othello says that he hopes his kisses are the closest thing to fighting that they ever come to. This is Ironic because Othello will end up killing her. 

Amen to that, sweet powers!
I cannot speak enough of this content.
It stops me here, it is too much of joy.
And this, and this, the greatest discords be (kissing her)
That e'er our hearts shall make! Act 2 sc 1