this is mostly why sylveon will never be too great. if it runs shadow ball, it either drops being a cleric {heal bell}, being able to do real damage {calm mind}, or an important part of its healing {wish/protect}. common, powerful 'mons shit on it {aegislash, scizor, lucario}, and it can't really switch in on powerful physical attackers without maximum investment, and even then, hits will do a shitton, particularly se ones. it's a very "slow" pokemon, in the sense that it robs momentum {and literally!}, and can be setup fodder if it's not being powerful enough with its moveset and investment, but then it's often too slow to sweep unless the foe is a dumbass and lets it get to +6 or something, and it misses out on its greatest niche as a bulky cleric. probably some of the worst 4mss of this gen, for sure.