Intro:

This build focuses on farming creeps and doing heavy AoE damage in team fights. You'll most likely top the siege damage and XP contribution points.

Talents:

Seasoned Marksman is the core of every carry hero. Kerrigan is one of the strongest utilizer of this talent because of her cleaving attacks she can farm creeps very fast. You can easily take out camps and creep waves buffing up your damage output.

Battle Momentum allows you to spam your skills which then empower your auto attacks with Double Strike.

About her skills:

(E) Primal Grasp helps you clear camps and creep waves faster and lets you catch up with fleeing heroes. Always spam this on creeps and when pushing and also in team fights to CC your enemies.

(W) Impaling Blades is your utility skill. Drop at the middle of a team fight and when engaging in 1v1s. If your opponent tries to flee you can pull him/her back with E. W has about 1.5-2 seconds delay after cast, so you'll need some practicing to get used to the exact timing.

(Q) Ravage is a strong chasing ability. It also lets you jump into fights after the tank of your team initiated. While channeling Maelstrom, it helps you reposition in the teamfight to quickly finish off squishy heroes.

Her 3 basic abilities together makes Kerrigan one of the strongest chaser. After taking Battle Momentum you can spam all skills while fighting both creeps or heroes. They have low cooldown and low mana cost.

(R) Maelstrom is an extremely strong AoE that with in combination with your trait Assimilation makes you the most tanky melee carry. The enemy team has to focus you in order to take you down. Even if you fall they are sure to follow and 1 for 5 is a very good trade.

Note:
I played this build with my friend in combination with Abathur. He copies Kerrigan which results in insane AoE presence by double cleave damage and Abathur's own AoE spell while buffing up Kerrigan with an extra shield. The synergy between these 2 heroes are very strong.