Mordekaiser is an very old champion,and even after recent rework(and latest nerfs) he seems to remain in dust. I think these changes can help him to get on same level with the latest tendencies in champion making/reworks(Fiora being the best exemplar)
So here is my suggestion on changes for his kit:
Q: ACTIVE: Mordekaiser's next three basic attacks deal bonus true damage. The final strike does 2 times the bonus damage of the previous strikes.
FIRST / SECOND HIT BONUS TRUE DAMAGE: 2.5/5.0/7.5/10/12.5% of target's maximum health (+ 50 / 60 / 70 / 80 / 90% AD) (+ 60% AP)
THIRD HIT BONUS TRUE DAMAGE: 5/10/15/20/25% of target's maximum health (+ 100 / 120 / 140 / 160 / 180% AD) (+ 120% AP)
W:Changed second activation: Mordekaiser now can cast it to instantly teleport to affected ally's location
R:Total Damage: 25 / 30 / 35% (+ 4% per 100 AP) of target's maximum health in magic damage ->25/30/35%(+4% per 100 AP) of target's maximum health in true damage
I plan on adding same topics for other old champions,which I think would help them reach balanced state.
Thank you for your attenion!
With best wishes, Neverspring