Malbim: They will go to many punishments destined for them.

Rashi citing Bava Basra 8b: They are in increasing order of severity. Death via the sword is more than disgraceful than Stam death (on one's bed) - "Yakar b'Einei Hashem ha'Mavsah la'Chasidav" (Tehilim 116:15). [Death due to] hunger is worse than death via the sword, for the former is pained [for much time], and the latter is not - "Tovim Hayu Chalelei Cherev me'Chalelei Ra'av" (Eichah 4:9). Captivity includes all of these.

Malbim: Maves and Ra'av are via beings with choice. Cherev and Shevi are via beings with desire ¹ , e.g. dogs and Chayos (verse 3). "V'Shen Behemos Ashalach Bam...; mi'Chutz Teshakel Cherev" (Devarim 32:24-25). It is as if once they left Hashem, four punishments are prepared for scoffers - "v'Hayah ha'Nas mi'Kol ha'Pachad... [veha'Oleh mi'Toch ha'Pachas Yilaked ba'Pach" (Yeshayah 24:18), "Ka'asher Yanus Ish mi'Pachad ha'Ari..." [u'Fga'o ha'Dov]" (Amos 5:19).