Dawnbreaker + Silencer

Why this works

Teamfights breaking out across the map become a nightmare for the enemy. Silencer can cast Global Silence from anywhere, creating the perfect setup for Dawnbreaker's Solar Guardian. Enemies are suddenly unable to cast spells to escape or counter-initiate as Dawnbreaker lands with a stun and heal. This complete lack of enemy spellcasting also guarantees Dawnbreaker a free, uninterrupted channel of Starbreaker on multiple heroes. Last Word on a key target further locks them down, preventing them from using a defensive item or spell to survive her initial burst.

This global threat forces the enemy to play cautiously as soon as both ultimates are available. Grouping up for an objective becomes a huge risk, as the combo can turn a simple push into a team wipe. The counterplay involves trying to bait one ultimate without the other, or having spell immunity active before the silence even hits, which requires incredible prediction. Otherwise, the enemy team is forced to split up and cede map control, allowing Silencer and Dawnbreaker to set the pace of the entire mid-game.