How much worse punishment do you think one deserves ... grace?

"This was severe punishment. But the punishment will be even greater for anyone ... grace!"

who has trampled underfoot the Son of God

"who has rejected the Son of God"

"by treating the blood of the covenant as unholy"

Here "blood" stands for Christ's death, by which God established the new covenant.

"the blood by which God sanctified him"

"the Spirit of God, who provides grace"