Fake Messiahs.
Jesus answered them, Be careful that no one misleads you [deceiving you and leading you into error]. 5 For many will come in (on the strength of) My name [appropriating the name which belongs to Me], saying, I am the Christ (the Messiah), and they will lead many astray. (Matt 24:4-5, AMPC)
Jesus told them, “Don’t let anyone fool you. 5 For many will come claiming to be the Messiah and will lead many astray. (TLB)
Jesus said, “Watch out for doomsday deceivers. Many leaders are going to show up with forged identities, claiming, ‘I am Christ, the Messiah.’ They will deceive a lot of people. (TMG)
When the disciples asked Jesus when the last days would be, the first thing He told them was versions of Himself. Usually the first thing you tell someone when warning them is the most important one and you would think the big disasters would top the list. But being deceived by fake Messiahs is how He leads the list.