In Christianity Jesus shows unconditional love on the Cross. God's love is equal and infinite for all of us. The hindrance is that we don't recognise this and prefer the world of the conditional. In Buddhism the Middle-Path points at avoiding extremes. For the mind attached to the conditional, the world seems to always change. Whatever we have found that we like or don't like it never seems to last, we are left either missing it when it goes or wanting to change it because it won't go. Thus we live a life of struggle and suffering being tossed around on an ocean (often called Samsara). The Middle Path lies between these extremes of having and not having, between attachment and rejecting. That is where the unconditional lies in Buddhism.
Its fairly easy to arrive at the conclusion that all things are conditional or relative. If there was a continuous hum in our ears that never changed we would never become aware of it. If we made machine that could measure it we would calibrate them to that zero was this hum. It would be undetectable, unmeasurable. The conditional mind is like that of reptiles: we sense and are attracted to change--the excitement of finding something, the need to get rid of something. We live in the space between things. When we are thirsty we like to drink, but soon that thirst goes and we become quenched. Then we are bored again and onto something else. Always moving like a snake, sewing our lives between the opposing things of the world. This is actually suffering, we never go anywhere or become anything. Ultimately the journey is pointless.
Likewise in Christianity we are in a state of eternal Sin after we forbade God in the Garden of Eden and were banished from his protection to work and struggle for our living. We rejected the unconditional and were forced into the conditional. Sin is missing the mark, not thinking and behaving true in accordance with God. That is not behaving with insight of the unconditional and being swayed by the condition. As a simple example Greed is taking more than we need. Equally "Miserliness" is taking less. As Buddha discovered you cannot beat greed by starving yourself to death: that is incredibly naïve; that is still conditional thinking. To beat Greed you must beat Miserliness as well: these are the extremes and the conditional mind swings between them. Actually why don't we just take what ew need? That is the end of suffering, and the end of Sin.
So why don't we just take what we need? We are like that snake slithering between things, or the lizard only seeing movement. As conditional minds we only see the changes. We don't see the satisfaction of having taken what we need, we enjoy the process of satiation instead. And when we are satiated then we try to satiate a some more and eat some more when actually we don't need it. This is why all religions point at the same things: appreciation, gratitude, kindness, love, joy. When we eat just what we need we appreciate the gift of the food that nourishes our body; we have gratitude to the world and the people who have supplied this food; we are kind to our bodies that need the food and the world that must supply that food (non-meat eating is a natural progression); we love both ourselves, others and the beautiful world that has such a thing as eating and food in it; and we are joyful to abide in such a world. By contrast the Glutton and the Miser have no joy in what they gain, they seek only the momentary pleasure of eating or of denying themselves, they do harm to both themselves, others and the world. This is sinful and achieves nothing but a life of suffering.
So what is the Unconditional? This is a question best not asked. Whatever we say will be conditional. The conditional is characterised by birth and death, that is creation and destruction. Nothing lasts forever and nothing has been in existence forever. Take a feeling that we have: you will be able to say when it started and you can we 100% sure it will end (pretty soon in the case of feelings - they are very fleeting). Every part of our minds is changing very rapidly. This is the "burning house" that Buddha spoke of, every single part in flames and changing. Even the words I write here take me only a half hour to write, and less to read and will be out of mind in no time. Hopefully they say things about the world that have greater longevity but even these ideas come and go. Buddha said even Buddhism has a shelf life. This is why we must take urgent steps to escape the sea of Samsara while we have the chance, gain that crucial scrutiny of the conditional so that we can unhook leaving only the Uncondition or God.
But what is the Unconditional if we wish to push this. Note this is a dangerous path because suppose we did identify the unconditional while still having a conditional mind we would immediately attach to it: "Ah! Look I have found the Unconditional" we would feel to ourselves and immediately we would reject everything else. Yes the Unconditional is not relative to other things, it has nothing to reject and so it has nothing to attach or attract to. There is no "truth" in this sense. Its not like a argument over the colour of Morpheus Butterfly. The person who say Blue is correct, they can get a gold star and a point, and the person who say Green gets nothing. But this is conditional and relative truth. You can be right or wrong. Unconditional Truth just is: no right and wrong. God cannot be wrong cos he cannot be right. He just is. But as mentioned there are things that are characteristics of the Unconditional like Kindness, Love, Gratitude, Patience, Frugalness, Equanimity and Even-Mindedness. If we perfect these we find that we rise slowly out of the turbulent seas of the conditional and the snake instead of moving around things starts to move through things and we stop noticing the change so much as abide in the peace at the heart of things.
Now the one thing I am unclear about this this analogy. The conditional mind is like the weather. Some days it is rainy and some days it is sunny. In other words, crudely, some times good things happen and other times bad things happen. But while the weather is always changing the Sun always shines constantly in the sky. While the changing weather is the conditional, the unchanging Sun is the Unconditional. Now what I don't understand is whether the "happiness" we feel when things are going well is a window into the Unconditional, but we experience that core nature of the world through a conditional lens. In other words when we finally give up the conditional and stop looking at the weather and just accept the good days and the bad days as relative and unsubstantial are we then basking in the Sun. Or does letting go of the opposing good and bad days and being dragged this way and that enter us into a different world than we even got a glimpse of on happy days. Are "good times" in our ordinary worlds of suffering a glimpse of the Eternal or is all such worldly attached experience part of the conditional. In Yin-Yang terms whole the Black and White oppose each other, the Dao is neither Black nor White, nor Black and White, not etc etc. But this is irrelevant as the actual task is just to enter the middle path and make our arrow true and Sinless.
This is religion.