- Any Mega Evolution that lowers a stat always puts at least that many points into its less used offensive stat. For example, Mega Camerupt loses 20 points in Speed, but it also gains 20 points in Attack; Mega Abomasnow loses 30 points in Speed, but it gains 40 in each of its offenses, some of which will almost certainly go to waste no matter how you choose to invest; and Mega Mewtwo Y loses 20 points in Defense, but it gains 40 useless points in Attack. The point I'm trying to make here is that losing points is not used as a way to cheat the +100 limit but actually as a way to weaken a Pokémon - those extra points are fairly consistently
thrown away rather than amplifying the Pokémon's best stats even more.
- Something like Mega Sableye might appear to be an exception, but it typically uses neither of its offenses - its -30 Speed is "compensated" with boosts to both Attack and Special Attack that still add up to 30, and its more relevant Defense and Special Defense stats still don't exceed +100 and would be just as possible with no change to its other stats at all.
- One of the only real exceptions to this is Mega Diancie (which loses a significant number of points from two important, relevant stats in its defenses - its Mega Evolution is a total role shift, not just trying to get better at the same thing by cheating the +100 limit) - and while none of its other stats really count as throwaways because it uses all of them, the fact that these boosts are split equally between its offenses rather than committing to one is still a relevant way to keep it in check. (Imagine a Mega Evolution that had -80 like Diancie and actually tried to optimize for one role! It would be ridiculous.)
- The only other cases that break this "rule" are Mega Heracross - which loses a mere 10 points from the very relevant and important Speed stat and actually does put those 10 points towards other relevant stats - and Mega Beedrill, which... is Mega Beedrill. I'll cover why Beedrill is an exception next, in fact!
- The other "rule" about Mega Evolutions is that they only ever lose points in
Defense, Special Defense and Speed - as I've said, these are
relevant stats that affect a Pokémon's performance no matter what kind of set it chooses to run. If a physical attacker loses Special Attack, this is inconsequential for any set that doesn't use special moves; heck, if a special attacker loses Attack, that's even an actively good thing on some level. But this
doesn't happen - they only ever lose Speed and bulk, each of which actually impacts the Pokémon in specific matchups no matter what kind of set it's running. A Pokémon is always
actually affected in some way by being slower or by losing bulk - it can't just change the moves it runs and see no difference at all.
- As mentioned, I now need to talk about Beedrill, which is the only Pokémon to be an exception to both of these "rules." Here's the thing about Beedrill - it has a base stat total of 395, one of the lowest of all Mega Evolving Pokémon. Even if it didn't lower its Special Attack at all and just had a +130 BST boost instead of +100, it would still only have 525 - barely even above average for a fully evolved Pokémon, let alone a Mega Evolution. It's clear that Mega Beedrill is an exceptional case and not a precedent that just any Pokémon can follow... and even that was +30, not +80!
(And even then, it's still Mega Beedrill. It's a pivot with a Stealth Rock weakness, it's an Adaptability user with terrible STAB, and it has base 145 Speed but it's one-hit KOed by nearly every unresisted priority move. Even with the +60 boost to its Attack in conjunction with Adaptability, its damage output is still relatively average for an offensively oriented Mega Evolution. Basically, try to keep in mind how bad Mega Beedrill would have been if it didn't "cheat" like that.)