To provide the best guide, it helps to narrow down which "Assassin" you are looking for. Since this is a popular archetype in gaming, here are top guides for the most common versions:
Synchronize Deathmark and Kingsbane for massive burst phases. 🎲 Dungeons & Dragons (5e) / Baldur’s Gate 3 assassinator
Keep Garrote and Rupture active on your primary target. To provide the best guide, it helps to
Use the reworked Crimson Tempest to spread bleeds to multiple enemies. To provide the best guide