There are two forms of unconditional love. One is localized, for example loving a child, pet, parent or partner unconditionally. This means, whatever will happen, I extend myself for the purpose of nurturing your material and physical well-being, as well as your learning, healing, growing, and awakening. It is extended without expecting anything in return and thus unconditional. However, this love is not extended in the same way to others, and thus localized. It also implies that if your love is abused, if someone takes advantage of you, refuses your love, or uses it in self-destructive ways, you will no longer extend yourself, as this would obviously not nurture their well-being, etc. and thus not be loving. Giving an alcoholic alcohol, or a junkie money is not loving but co-dependent. In other words, to love unconditionally has no room for abuse.
The other form of unconditional love is universal and includes ourselves. It is the unconditional acceptance of everything that arises moment to moment in our awareness as it is, without judgment, desire, attachment, hatred, or fear. In spiritual terms, this is called full surrender and awakening to what is by being fully present.
Both can be seen as ideals to strive for. Nobody that I know of is perfect. There is also no end, as our inner and outer world, including our relationships, constantly increase in complexity (and also freedom) and along with it the challenge to love unconditionally.