The best replacement for unholy is frost.

The best alternatives to unholy are rated as following:
★★★★★  frost
★★★  frost pvp 5.4
★★  blood
★★  frost death knight
★★  frost dps
★★  frost pvp
★  frost 4.3
★  blood dk
★  frost leveling
★  frost dk 5.4
★  holy dante's inferno
★  frost dk pvp
★  frost for dps
★  frost mop
★  frost dk
★  holy
  blood dps
  frost for pvp
  frost pve
  blood presence
  frost 5.4
  frost cataclysm
  frost presence
  blood pvp
  frost 5.1
  frost 5.2

Your alternative for unholy is not listed? Suggest!
Speaking about unholy, one probably shouldn't forget about obliterate.

Other search terms related to unholy and their ratings are:
★★★★★ obliterate
You have in mind a companion for unholy and it is not yet here? Propose!



Google Trends

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unholy
frost
frost pvp 5.4