periphetes- Theseus hit periphetes with a bronze club as that's what periphetes killed others with
sinis- Sinis, an Isthmain, killed travelers by tieing them to two pine trees and bending them to the ground. Theseus killed Sinis by using the same method on him! He tied Sinis to two trees and used the momentum of the trees to bend him to the ground.
The crommyonion sow- north Isthmus was terrorized by a monstrous wild pig, named the Crommyonian Sow. This sow belonged to Phaea, who was an old witch. Theseus killed the Crommyonian Sow and its mistress as soon as he arrived in Crommyon.
sciron- He would kill travellers that were passing through these rocks by forcing them to wash their feet and then kicking them over the cliff. Theseus tricked Sciron by telling him to wash his feet. When Sciron bent over to do so, Theseus kicked him over the cliff.
cercyon- Cercyon, was a strong man who challenged those passing through his lands to a wrestling match, passing through the roads around Eleusis. Although he promised to give his kingdom to the winner, the losers weren’t safe – they were killed. As you can imagine, there were never any winners! Theseus defeated the king skillfully instead of using his physical power and captured his kingdom after killing him.
procrustes- Procrustes, controlled the path between Athens and Eleusis on Mount Korydallos, Erineus. He invited all those who traveled his way to help him with a blacksmithing task, which often resulted in the deaths of those who tried to help. Instead, Theseus beheaded him along with cutting his legs with his own axe.