Malphite is an incredibly strong counter-pick against AD melee and ranged top laners, but avoid first-picking him due to his numerous counters.
Focus on tank itemization when facing AD champions; his E's attack speed slow is highly effective, and his Q deals surprising damage even with a tank build.
Sylas is a major counter, so consider banning him. Be mindful of specific counters like Grasp Gragas or certain AP champions that can challenge you.