First, the Cyclopes are described in the very beginning as "dealing out rough justice to wife and child." Obviously if they have no problem treating their families violently, they would probably have no problem treating a stranger with violence.
Second, when the Cyclops came home, he used a big rock to cover the entryway. It is at this point that we realize that Odysseus and his men will not be getting out. This foreshadows that there will be a confrontation for them to get out.
Lastly, when we learn that Posideon is the Cyclops' father and that Odysseus messed with the Cyclops' and add to that that Posideon is the god of the sea where Odysseus needs to travel, we can anticipate that Odysseus will have problems.
These are the instances I see in the Cyclops section. It may be that you were looking for something else and another editor might point it out to you.