Up to 5-20% Strength based on the charge time of your heavy attacks. Stacks 3 times.
5-8% Strength for 4.5s on Kill. Stacks 5 times.
7-10% Strength for every 4 Single Target Hits. Lasts 2s and Stacks 5 times.
5-6.5% Strength for 3.5s on Close Range Kill.