Wiki linked below as well as my preferred debuffs list
https://wiki.melvoridle.com/w/Impendi...
These are the least worst
+20% Maximum Hit and -10% Maximum Hitpoints
+20% Maximum Hit and +20% Accuracy Rating
+2000 Maximum Hitpoints and -10% Maximum Hit
+50% chance to apply poison when hitting with an attack and +10% Maximum Hitpoints
+15% Damage Reduction and +15% Global Evasion
+100% chance to ignore Slow effects and -5% Attack Interval
These are the ones I avoid at all costs
+50% Chance to apply burn when attacking and +50% chance to apply frostburn when attacking
+10% Maximum Hit, -10% Attack Interval, and -10% Global Evasion
+15% chance to apply affliction when attacking and +15% Lifesteal
Slayer Area Effects are 5% Stronger
Heal 4% of current hitpoints every 2 turns and +40% of Maximum Hit added to Minimum Hit
+100% chance to ignore Stuns and Freezes and Immune to Sleep