Why not begin by making a t chart and listing points of agreement on one side and disagreement on the other. This will help you choose a side. Then, once you have chosen the stronger side, or the side with more points, you can devise a thesis based on whether you agree with this statement or not. Use your points as evidence.
If I could just add a little to post #3, once you have decided whether you want to challenge or defend the statement, try to provide at least one personal experience example along with a variety of others from histroy, culture, current events, etc.
Also, if the purpose of this essay is to develop your argument skills, you need to make a concession--a point which you concede (agree with) to those on the opposing side of your argument. This demonstrates that you are a logical thinker and that you have thought about why others would not share your opinion. If you never consider why your opponent thinks what he does, then your own argument and side will suffer.
When an instructor assigns an essay with this type of statement, the writer is expected to either defend the statement or refute it. What you need to do first is decide whether you agree or disagree that reality is irrefutable and inescapable. Once you decide where you stand (and no fence straddling allowed), then write down a statement of agreement or disagreement. Then you can ask yourself WHY you feel this way. Jot down those thoughts and ideas, because they will form your supporting paragraphs later. Can you think of any examples from literature, films, politics, popular culture, and/or history that show that your position is correct? Write those down too.
Congratulations—you have just brainstormed for your essay!
The first question is whether you have to support the idea or go against it. I am not able to fully grasp where you have to go with it. Regardless of which way you go with it, your answers might best come from literature, film, or perhaps even real life. This will depend largely on what you have experienced in your own reading or viewing and interpreting that in this setting.
If you are going to go in support of this, your fundamental premise is that reality is cruel and harsh, and there is little way to escape such a condition. I would search for examples of individuals who are left without any escape from their reality. It confronts them and no matter what, they are stuck with what is. You might want to look at characters in literature who seek to escape or transcend their reality in dreams or hopes and what happens when these are not realized. This is a common theme in literature, and much depends on what you have read. You can also find this in films, again, depending on large part of what you have seen. History and real life have plenty of examples of this. Think of people that have been the victim to senseless slaughter and violence. There was no escape for them and reality is quite unforgiving. When a child is washing her family dog outside her home and is a victim to a stray bullet from a drive- by shooting, there is little else but to say that reality is unforgiving and this reality haunts us as there is little escape from it. Another example is the atrocities committed in Darfur or other regions in the world where there is little else but to suggest that reality is unforgiving. We can even look at our own states of being. Children being abused, partners being tormented through abuse from ones that supposedly love them are local examples of how reality is unforgiving.
If you are going to go the opposite in suggesting that reality is not unforgiving, you would be looking for examples of how individuals can overcome a harsh reality or set of conditions. In these cases, there is a note of hope and positivity to counter the harsh condition of reality. Here, again, we can find literature to assist us. Dante's Divine Comedy is an example of a spiritual pilgrim who must, in the course of Easter Weekend, undergo the inferno of hell, the purgatory, and the eventual claiming of paradise to understand what it means to be closer to God and identify a higher sense of self. Shakespeare's sonnets on love are excellent examples on how individuals can transcend their difficult conditions with love and belief in someone or something else. Film has many examples of this theme, also. History, while often depicting something of brutality and harshness, features individuals who defy that reality is an unforgiving existence without escape. Listen or read the speeches delivered by Elizabeth Cady Stanton and Susan B. Anthony or Frederick Douglass, both articulating that there is a way out of a reality carved with the knives of sexism and racism. The narrative and election of President Obama is also a testimony to how reality is unforgiving, but one where escape from these conditions is possible. Elie Wiesel is another example of someone who has seen reality at its most unforgiving as a prisoner of the Nazi Death Camps. It's a fascinating topic and I think a strong approach either way will yield a potentially great essay.