(For many walk, of whom I have told you often, and now tell you even weeping, [that they are] the enemies of the cross of Christ:
Note 3 at Php 3:18: It is not clear to us who Paul was speaking of in these verses. Paul didn't give any explanation, because it was probably obvious to the Philippians to whom he was writing. They could have been professed Christians who were either legalistic or, on the other extreme, indulging in sinful pleasures. They are described as "enemies of the cross," which implies "error" in doctrine or lifestyle. Vine's Expository Dictionary describes "error" as "a wandering, a forsaking of the right path...whether in doctrine (2Pe 3:17 and 1Jo 4:6), or in morals (Ro 1:27, 2Pe 2:18, and Jude 11), though, in Scripture, doctrine and morals are never divided by any sharp line."
Further descriptions revealed their bellies as their god; this means they were led by their own fleshly desires and appetites. They gloried in that which they should have been ashamed of, and their hearts and minds were set on the things of this world. Paul wept as he declared their end being destruction. Paul often warned God's people of such deception (1Co 6:9-10, Ga 5:21, and Eph 5:5-6).
Note 4 at Php 3:18: The people that Paul was speaking about were the "enemies of the cross of Christ," yet he wept when he spoke of their destruction. That says a lot about the Apostle Paul. Paul was ruthless at times in defense of the Gospel, but his anger was not really against the people; rather, it was against the error they promoted and the damage it caused. Paul himself loved those who opposed him, even to the point that he said in Ro 9:3, "I could wish that myself were accursed from Christ for my brethren, my kinsmen according to the flesh" (see note 3 at that verse).