I want to remove ice beam from luvdisc in gen 7 random battles.
Luvdisc's role in gen 7 is primarily to enter the field, outspeed the opponent using its extremely high 251 speed, and use either scald or toxic to attempt to spread status. Even at level 100, luvdisc only reaches 137 special attack, and needless to say this is not enough to break anything purely off of the power of your attacks. because of this, luvdisc's successes generally involve clicking toxic and then stalling out the opponent. Substitute is so crucial because luvdisc happens to be the perfect abuser. with it's speed, you can outspeed almost everything, and after applying toxic you can simply alternate between substitute/protect while losing only 12.5% each turn after leftovers healing. Ice beam always replaces substitute, so you can still stall with protect, but because you can't reliably click protect multiple times in a row, you will take hits you would not need to take with substitute - something so important to a pokemon with the well below average bulk of 248 HP/167 Def/187 SpD
tl;dr luvdisc is a toxic staller and needs substitute to effectively fulfill it's role, and ice beam is not powerful enough to replace substitute