Curse of Weakness (rank 2)

• Demon SkinLevel 1 · Rank 1
• Fel ArmorLevel 1
• Infernal ArmorLevel 1
• InvocationLevel 1
• Shadow BoltLevel 1 · Rank 1
• Shadow CleaveLevel 1 · Rank 1
• Soul LinkLevel 1
• Summon ImpLevel 1
• Blood PactLevel 4 · Rank 1
• CorruptionLevel 4 · Rank 1
• Curse of WeaknessLevel 4 · Rank 1
• Life TapLevel 6 · Rank 1
• Bane of AgonyLevel 8 · Rank 1
• FearLevel 8 · Rank 1
• Create HealthstoneLevel 10 · Rank 1
• Drain SoulLevel 10 · Rank 1
• Summon FelguardLevel 10
• Summon VoidwalkerLevel 10
• TormentLevel 10 · Rank 1
• Health FunnelLevel 12 · Rank 1
• Curse of RecklessnessLevel 14 · Rank 1
• Drain LifeLevel 14 · Rank 1
• SacrificeLevel 16 · Rank 1
• Consume ShadowsLevel 18 · Rank 1
• Create SoulstoneLevel 18 · Rank 1
• Curse of the ElementsLevel 20 · Rank 1
• Demon ArmorLevel 20 · Rank 1
• Lash of PainLevel 20 · Rank 1
• ShadowburnLevel 20 · Rank 1
• Summon IncubusLevel 20
• Summon SuccubusLevel 20
• Eye of KilroggLevel 22
• Soothing KissLevel 22 · Rank 1
• Drain ManaLevel 24 · Rank 1
• SufferingLevel 24 · Rank 1
• Curse of TonguesLevel 26 · Rank 1
• Detect InvisibilityLevel 26 · Rank 1
• SeductionLevel 26
• BanishLevel 28 · Rank 1
• Devour MagicLevel 30 · Rank 1

And 18 more.

The free addon pack puts it on your bars, or see the whole Warlock spell list.