Pain cycle's enchantment description normally says that:

• At tier 1, it triples damage
• At tier 2, it quadruples damage
• At tier 3, it quintuples damage

However, this effect diminishes when combined with other additive damage buffs, such as reckless, strength, cowardice etc. resulting in pain cycle giving less damage than it's supposed to.

So at tier 1, pain cycle adds +200% damage. At tier 2, it adds +300% damage, and at tier 3, it adds +400% damage.

For example:

• Without strength, the base damage is 100. When pain cycle (tier 3) triggers, 400 damage is added, resulting in 500 damage, which is the correct amount of damage.
• With strength, the base damage is 200 (100 base damage + 100 extra damage from strength). When pain cycle (tier 3) triggers, the 200 base damage is not quintupled, but only 400 damage is added, resulting in 600 damage. That is only triple the base damage, while the correct amount of damage should be 1000.