Do we have sympathy for Grendel in this chapter? He does enter the mead hall and kill two thanes. Then, he returns and kills a guard.

Which chapter are you referring to?

chapter 4

Grendel's inability to communicate with the villagers, despite his own ability to understand their speech, serves to connect Grendel to the human world while at the same time placing blame for Grendel's "monstrosity" more squarely on the shoulders of the culture that rejects him. Grendel cannot help that his words come out as guttural howls, but the people connect this miscommunication with his appearance and form a judgment upon Grendel on the spot. Even later, when certain warriors and a priest demonstrate that they can in fact understand Grendel, it is too late. Grendel has been branded a monster, and a monster he will continue to be. So, yes the monster can't communicate. I do sort of feel for him. The isolation and loneliness would drive any monster crazy!