This is my favorite way to play Kayle (there's little that's more fun than evaporating an adc with 1 Q and 1 attack). I can vouch for its effectiveness in solo queue - it got me to platinum. It is _not_ the safest way to play Kayle, and the strategy _is_ snowbally, so be advised that some games are likely to be awful (these are balanced by ones where you feel like you can blow anything up on command).
The main idea is to assert heavy lane dominance in the early game. You start the game with 56 AP, which gives you just over 100 damage per attack. At level 2, you get a slowing nuke that starts things off with another >100 damage spike and lets you land several attacks. Very few people will expect your damage at early levels, and fewer will be able to handle it.
- Lane bully
- Strong nuking powers
- High utility from her ult and W
- Can be played from multiple lanes
- Gankable while bullying
- No hard cc
She has heavy weaknesses that are mitigated by experience with her. She has strong advantages that are greatly amplified by experience in particular matchups. Her ult requires experience in teamfights as Kayle against different team compositions. A player can choose to play Kayle almost exclusively (she is strong mid/top and a situational support).
All of this combines to make her especially well-suited to a champion specialist - I don't recommend dabbling with her.
Have fun and show no mercy.