RF10-15 + Freeze Mobs + Magnetize Mobs is the safest combination.

Some tips include still casting your Bursts and Skills while frozen but turn off RF before doing so if you want more legit numbers for showcase purposes (or if you want to show screenshots of Challenge Summary if you're selling accounts, for example).

Do not rush Abyss, clearing the highest Level within few seconds is unrealistic and the game developer of course know and see that in the stats.