If I was forced to teach just one attribute of God, I would chose His love.
There is a path to all of God's other attributes from the love of God. Especially if you remember that the love of God is, first, trinitarian. It's the Father's love for the Son, the Son's love for the Father, and the love of the Spirit as well.
Well, I wouldn't want to teach one of God's attributes, but if I were forced to teach one of God's attributes, I think I would choose the attribute of the love of God. Now, theologians argue about, does God have a primary attribute? I'm not asserting that about the love of God. I just do think, however, that there's a path into all of God's other attributes from the love of God. Especially if you remember that the love of God is first Trinitarian.
It's the Father's love for the Son, it's the Son's love for the Father, it's love of the Spirit as well. And so some people think, well, we don't want to say God's love is primary because then We're not doing justice to his holiness. Well, I would argue that there's a way to understand God's holiness as God's infinite and holy love for himself so I Think I would teach them the love of God so long as I was able to start with the idea that this love is first Trinitarian. God's love is not, first of all, his love for mankind. God's love is, first of all, his love for himself and the interpersonal love of the persons of the Trinity for each other.
And since the Father's love for the Son is primary and infinite and eternal, if people get in the way of His determination to exalt his son, then that's where God's wrath and holiness come in. So I think I would choose the love of God.