Possible to sue companies for lack of security/support?

Ugh. Same old song and dance.
Ignorance abounds.

Snor, you're fine.
For the record, you can sue a company for failing to protect your private information.
On the "customer support" end, I'm sure you could, in theory, but I have no idea where the line would be drawn.
Customer support is generally a nicety to encourage continued patronage or to prevent issues from getting to the class-lawsuit level and is rarely a contractual obligation.

Just a bit of information, regarding:

Like I said, I don't know what they wrote in their Terms of Service regarding sueing. Sony did this recently, as well.

Even if Nexon had a clause saying "you cannot sue us", it wouldn't necessarily matter.

You can't go to a restaurant, order food, and then sue them because their service sucks.
Your account is property of nexon.

Depending on how the service "sucks", you certainly can.

You account being Nexon's property doesn't excuse them from being guilty of negligence.

Account is property of Nexon, and it is your responsibility to keep the credentials secure.

Psychpillow, is that you?

What utter bullpomegranate.
Even if a player does those things, certain aspects are out of the customer's hands.
Snor's question is about the latter.
Please don't post irrelevant dribble.

pretty sure you can... or maybe this is just me living in the U.S. too long

OH I GET IT BECAUSE THE UNITED STATES HAS SO MANY LAWSUITS!

This is what a judge would say to you
You can simply not play the dam game jesus

And you can simply choose not to eat at the restaurant whose poor health standards resulted in you getting horribly sick and incurring serious medical bills.

-more quotes from the ToS irrelevant to the question-

That bit from the ToS says they can take any action appropriate.
Snor's question is whether someone could sue if those actions were inadequate.

Not sure but, wasn't it said before that the TOS more than a shield that can protect them from any lawsuit was actually just there to scare people from doing it?

As with any ToS, it is presented as an absolute law while, in fact, certain aspects may be legally unenforceable.
Since the average human being wouldn't know this (as judged by posts I've seen across the Maple fandom), that would indeed protect them from some people who would otherwise contemplate legal action.

(See top part of this post regarding Sony's attempt to tell its customers that they can't sue the company.)