Early levels: lvl 5
3 in W:
110 + 80%AP
120 + 80%AP
-> 110
Pretty weak... but still deals ~400-500
ed burst. Although like most AP bruisers, the magic cat farms early game.
I'm assuming Lvl 9 rengo with and

- [(18 from runes)+ (14 from masteries) 320]•1.35 ability power = 475.2
DFG: 15% of target champion's maximum health in magic damage + 1.2 multiplier on all magic for 4 seconds
Lich: After using an ability, your next basic attack deals 75% base AD (+ 50% AP) bonus magic damage
Lvl 9 maxed W, 2 in Q, 1 in E
Combo: Dfg, W, auto, W, Q, auto, E
Double W deals:
(170 + 240 + 160%AP)•1.2 = 1404.384
Double Lichebane deals:
[80 + (60 + 50%)•1.2]•2= 874.24
Q deals:
144
E deals:
106
Total: 2528.624 raw damage (not counting resistances) [although you'll also have magic pen in your runes and masteries + start building towards void staff]
Not exactly leblanc... but it'll kill adcs at that level.
He's got no sustained damage... so that sorta sucks though
Edit: forgot to add the 15% health damage from dfg lol...