Attikus is an enormous target that can get caught on every nook and cranny, trying to escape an enemy often leads to getting stuck and killed. Due to his large size he is easy to hit so when under the effects of a slow he is at greater risk of death as shots fired are nearly guaranteed to hit him. Like most of the large scale characters, smaller enemy players can simply run circles around him to avoid his melee and having no ranged attacks also allows ranged enemies and turrets to shred through his defenses without ever letting him get close.
My suggestions -
Barefisted Brawling: Increase the attack speed animation a bit and possibly make it so every hit with his right fist absorbs enemy shielding.
Charged Hook: When fully charged have it fire a ranged attack akin to El Dragon’s Dragonfire so he can deal with turrets and the like.
Hedronic Arc: add an immunity to slows for its duration or cleanse debuffs when it is activated.