Depends on if u need a defender or an attacker. If u need a defender i suggest bullseye, red skull, photon or serpent if can get him awakened (defo him IF u can get him awakened). But if u want an attacker i suggest jack, okoye or guardian (especially if u have a hulkbuster relic). All of these r great but ALWAYS rank up the champion u like the most. Overall i would recommend photon or serpent (again definitely him IF u can get him awakened)