Hesed is the main theme of the book of Ruth. There are various acts of hesed in the book:
But overlooked is the greatest act of chesed. When Machlon left Israel he sold his land. When Naomi and Ruth came back, they could get his land back if they paid for it. This process is called "geula". Naomi and Ruth didn't have the money to buy the land.
Normally, when a "goel" would marry Ruth he would get her land, provided he pays the current owner for it. That would be the case here. But since Machlon died childless, yibum must take place. The process of yibum means that the child born from Ruth will be called "by the name" of the dead father, Machlon, and be considered his son.
As his son, that child will inherit all the land of his father (in this case all of Elimelech's land since Chilion died) and not be counted as the goel's son. So, essentially, the goel is paying for land that will not be his. For example, if he had another first born son by another woman, that child would not inherit the land the goel redeems.
So the great Chesed is that Boaz marries Ruth, buys her land and gives it to her son, which although biologically his, is not considered to be his son.
In the end of the story, Ruth gives the child to Naomi to nurse, as if to say that the child should be considered Naomi's, as a replacement for her two dead sons. Technically Naomi would not need a yibum since she did have children, but Naomi acted above the letter of the law and symbolically transfered her son to act as a replacement for Naomi's loss. Another act of hesed.