Why do crits seem to do 4-5 times more damage?

Question

2 ridiculous crit-related situations happened to me in Black 2 recently:
1. PWT (last month)
I do not remember who I was battling, but my Metagross used Iron Defense at full HP, and the attack it received did little damage. I used it again, and it got a crit that did a LOT more damage and almost destroyed Metagross.
2. Route 1 (today)
I was randomly walking around, heading to see Colress, I went into shaking grass and found an unexpected Lv 59 Wigglytuff. I used 8 Ultra Balls on it, but I couldn't catch it. So I switched out my Lv 100 Kyurem and sent out a Lv 53 Zweilous. It used 4 Defense Curls in total and I used 5 Body Slams and paralyzed it on the 2nd one. Then I sent out my Lv. 100 Emboar after I halved its HP, but I still couldn't catch it. So I sent back out Zweilous and used another Body Slam, which killed the Wigglytuff with a crit. Body Slam never did that much anyway, even before Wigglytuff used Defense Curls!
What is going on?
Also, why is it much harder for me to catch any Pokemon now? It used to be very easy!

Answer 1

In generations three, four, and five, critical hits ignore boosts to a Pokemon's defense stat.
Source

Comments

Don’t critical hits also do that in gen 6 and 7?

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But Body Slam never did that much on Wigglytuff. Compared to the first hit, it was like 2.5x damage.

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2.5 is pretty close to 2. In that case, it's probably something to do with how the game rounds damage when displaying the HP bar.

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And there’s the random 80-100% (not sure what the exact number is). You could’ve rolled low on the first hit and high on the second.