If you speak critically to someone such as "'You fool,' [you] shall be guilty enough to go into the fiery hell" (Mt 5:22). This would be punishment. It is God who judges "for a fire is kindled in My anger, and burns in the lowest part of Sheol" (Dt 32:27). "Death and Hades were thrown into the lake of fire" (Rev 20:14). "Geenna" is the Hebrew word for hell. It is at the Valley of Tophet near Jerusalem where they burned refuse twenty-four hours a day. You don't just get overtaken by the flames of a burning forest but can have "'your whole body to be thrown into hell'" (Mt 5:30). It is a literal place and not just a metaphor.
It is not good to overemphasize the "fire and brimstone" aspect at the expense of heaven and eternal life. "No one who is born of God practices sin" (1Jn 3:9). "The one who practices righteousness is righteous, just as He is righteous" (:7). However, "the one who practices sin is of the devil" (:8). Therefore, one overriding motivation of it all is that "the Son of God appeared for this purpose, to destroy the works of the devil" (:8). It is a practical matter and not just a philosophy or allegory.