Predecessor Builds > GRIM.exe > Grim Turret.EXE
Hide behind your frontline and melt everything. Focus on Grim's DPS instead of pure burst, and cover some of his main weaknesses.
Typhoon
Typhoon's dash gives you some agency and survivability, which can be especially useful as Grim can be painful to control when enemies are very close to you. It also helps you dash out of range after a trade, which can be a lifesaver due to his huge hitbox. This is especially true against certain supports with easy-to-hit CC.
Lightning Hawk
Grants high damage which works well for Grim's quick trade pattern, due to how his passive works. I prefer quick trades early, as his large hitbox and immobility makes long fights hard before he comes online. The passive also helps Grim kite and keep enemies at bay, as the slow from Assault Mode is only 10% (decaying) early game.
Adapting to the enemy team
Enemy support
If the enemy team doesn't have health stacking heroes, consider switching Sky Splitter for something else such as Tainted Rounds, Dust Devil,
Sustain
You're missing out on some lifesteal when going typhoon instead of a carry crest, so you might want to go Terminus or lane with a support that can heal you.