PoE2
Ruthless
Support
Melee, Attack
Requires: Level 1
Support Reqirements: +5 Str
Supports melee strikes, causing repeated uses to be more effective at Stunning enemies.
Every fifth use of this Attack causes 500% more Stun buildup
Place into a Skill's Support Gem socket in the Skills menu to apply its effects to that Skill. You cannot have multiple copies of the same Support Gem socketed at the same time.
PoE1
Ruthless Support
Slam
Support, Melee, Attack, Strike
Level: (1–20)
Cost & Reservation Multiplier: 120%
Requires: Level (1–70), (7–111) Str
Supports melee strike or slam skills. Every third time you use a supported attack, that use of the skill will be more powerful.
Every third Attack with Supported Melee Attacks deals a Ruthless Blow
Ruthless Blows with Supported Skills deal (70–98)% more Melee Damage
Ruthless Blows with Supported Skills deal (70–98)% more Damage with
Ailments caused by Melee Hits
Ruthless Blows with Supported Skills have a base Stun Duration of 0.8 seconds

Additional Effects From Quality:
Supported Skills deal (0–10)% increased Attack Damage
This is a Support Gem. It does not grant a bonus to your character, but to skills in sockets connected to it. Place into an item socket connected to a socket containing the Skill Gem you wish to augment. Right click to remove from a socket.