This adjective gets applied to all kinds of things these days — “The restaurant’s infamous chocolate cake,” “The team’s infamous victory over their rivals,” and so on — when what people actually mean is “famous” or “celebrated.” “Infamous” isn’t a compliment: It means disgraceful or having a bad reputation.
You can’t insure that something bad won’t happen. You can insure yourself — that is, buy insurance — so that you’ll be compensated if something bad does, but what you want to try to do is ensure that something bad won’t happen. “Ensure” means to guarantee or make certain; “insure” means to buy insurance or otherwise indemnify.
See “infamous,” above. “Notorious” sometimes gets used in the same way (“The restaurant’s notorious chocolate cake.”) But it doesn’t just mean famous — it means famous in a bad way, or known unfavorably.
This is the penultimate word in this list. And, no, it’s not the last one. The last word is the ultimate one; “pen-” is a Latin prefix meaning “almost,” and “penultimate” means second-to-last.
It sounds like something that tortures you, but that would actually be “torturous.” “Tortuous” means winding or twisting, like a road that curves up a mountainside.