Soraka has zero mobility, so she gets caught flat by Rakan's Grand Entrance (W) knockup and The Quickness (R) charm engage; her slow-landing Equinox (E) silence can't cut off his all-in, and she dies.

Sona has minimal mobility and a low base health pool, so before she can land Crescendo (R) she gets pinned by Rakan's Grand Entrance (W) and The Quickness (R) engage and instantly bursts.

Vel'Koz is an immobile poke champion, so once Rakan closes from the flank with Grand Entrance (W) and The Quickness (R) charm, he has no way out and gets caught and killed.

Light Binding (Q) is an aimed skill that Rakan can move around with Grand Entrance (W) and Battle Dance (E). After Q is down, he can close on immobile Lux and set up allied damage with The Quickness (R)'s charm.

Zenith Blade (E) is a linear skillshot, but landing it along Rakan's movement path roots him and carries Leona to the target. Shield of Daybreak (Q) and Solar Flare (R) can then lock him down before Battle Dance (E) disengages.

Nautilus's Dredge Line (Q) and the Staggering Blow (P) auto-attack root cut off Rakan's engage and escape leaps, and the guaranteed CC chaining into Depth Charge (R) locks him down completely.

Morgana's Black Shield (E) completely nullifies Rakan's The Quickness (R) and Grand Entrance (W) engage, and Dark Binding (Q) snags Rakan mid-leap.

Alistar's Headbutt (W)-Pulverize (Q) guaranteed knockup-and-stun combo is hard to dodge with leaps, and Unbreakable Will (R)'s damage reduction means Rakan can't win the health-trade fight.