Because of Karina’s speed and damage, she could chase and catch enemies at ease.
Well, use 1st skill. There are 3 reasons why this skill is great for Karina.
1. The 1st skill improves Karina's movement speed when she uses it.
2. Applying damage to an enemy while the skill is in effect slows the target's movement speed and
3. Karina becomes invulnerable from basic attacks for a couple of seconds.
Don't just frequently spam 1st skill. Always remember that enemy allies may be nearby and especially when you can't kill the target on time and you already used your 1st skill and it's cooling down and that means they could easily catch you so better think about it first beforehand.
Also, never forget to always target squishy heroes like mages, marksman or assassins, but remember not to be greedy as greediness could kill you.
After slowing down the enemy, use 2nd skill. Now the 2nd skill deals a lot more damage than the first skill so spam this instead to rapidly reduce the enemy's health.
Everytime you hit an enemy by the way, the passive activates too and stacking it to 2 times deals another damage to the enemy.
To deal the final blow, use 3rd skill. This skill deals a lot of damage to the enemy and what's more is that killing an enemy hero removes the cooldown of this skill so you could use it again. The animation of it is fast so reaching an enemy with it is super easy.
Some people use a different style of combo with Karina's skills
Like 3rd skill first then 2nd skill and 1st skill.
But well, it depends on how use her.