Guarantee a crit

Critical Weakness is applied after the fact.
You have 95% chance to crit with a 10% chance from crit weakness =
Roll for crit on attack -> fail to crit (5%) -> Roll for 10% crit chance from crit weakness -> fail to crit (90%)

If you conversion trap a diamond totem do you get 95% or 100%?

First, get a time machine.

Then go back to when Diamond Flasks.turned everyone to God for five seconds.

"

Critical Weakness is applied after the fact.
You have 95% chance to crit with a 10% chance from crit weakness =
Roll for crit on attack -> fail to crit (5%) -> Roll for 10% crit chance from crit weakness -> fail to crit (90%)

Wrong.

The crit mechanic is as follows:

Let's get back to that 1d100 for crit. If it's less than your crit chance, you crit. But this number is rolled on the monster, and takes your crit chance from the local value that the monster has for "player's chance to crit on me". Which is modified by CW and can go over 100%.