Amphinomus
Telemachus is made more confident to find Odysseus, and to drive out the suitors. (Neither of which he does.) Later, however, he does travel to Pylos and Sparta to learn of Odysseus' fate, and eventually, he assists Odysseus in killing the suitors.
they kill the suitors
Telemachus sailed away on swift winds, and the suitors were unable to catch him either when he left Ithaca or when he returned.
Athena
Eurymachus leads them all in their decision to ambush Telemachus.
It was Amphinomus who convinced the other suitors to put off killing Telemachus. He felt it was not right to harm someone who was the son of a king.
Telemachus is made more confident to find Odysseus, and to drive out the suitors. (Neither of which he does.) Later, however, he does travel to Pylos and Sparta to learn of Odysseus' fate, and eventually, he assists Odysseus in killing the suitors.
they kill the suitors
Yes. Telemachus fights his mother's suitors in both deed and combat.
the excuse that telemachus gives to the suitors is that he will clean the weapons
Telemachus sailed away on swift winds, and the suitors were unable to catch him either when he left Ithaca or when he returned.
The suitors plan to ambush and kill Telemachus upon his return to Ithaca to eliminate competition for Penelope's hand in marriage and to secure their own control over Odysseus's estate. They believe that by removing Telemachus, they will have a better chance of winning Penelope over.
Athena
Telemachus catches the suitors raiding the storeroom in his household.
Eurymachus leads them all in their decision to ambush Telemachus.
Odysseus tells Telemachus to hid the weapons so that the suitors can't use them. Telemachus has to say that the weapons are getting "smoke damaged" and he is afraid that the suitors will start hurting themselves with them if they have too much to drink.
Odysseus persuades Telemachus by revealing his true identity, proving he is still alive and capable of taking down the suitors. He reassures Telemachus that they have the gods on their side and that together, father and son, they can overcome the suitors' tyranny and restore justice to their home.