selach lanu abinu, ki chatanu, mechol lanu malkenu, ki pasha'nu,
In the 6th berakha of the Amida we ask HaShem Almighty for selicha/forgiveness.
We refer to God with two key words: abinu and malkenu
abinu means: 'our father' and it points out to the love God has for us, as our progenitor. God loves us as we love our children. We appeal to HaShem first as our loving father. Confident that no matter how bad we might have behaved, we know He will always take us back. Similar to a loving parent, all He requires to grant His forgiveness is that we admit our responsibility.
But God is also malkenu, our King. King is the ultimate authority. In ancient monarchies, Israel included, the King was also the supreme Judge and among other things, He had the power to sentence one to death. It is in this specific sense that we repeatedly refer to God as melekh during Yamim Noraim, when we realize that our lives are nowpending on God's imminent verdict.
These two words abinu/malkneu often stand at opposites sides. abinu refers to God as the One who granted us the gift of life and malkenu, as the One who can take life away from us.
The tension between these two words is solved at the end of this berakha: chanun hamarbe lisloach: HaShem is merciful, who forgives 'abundantly'. At the end of the day -we assert, and simultaneously wish for- God behaves to us as a loving Father, who keeps forgiving our mistakes once and again.