Bad days. We all have them; some of us deserve them. Here are five stocks whose naughty ways drew investors' scorn on Tuesday:

Company

Closing Price

CAPS Rating

(5 max)

%

Change

52-Week

Range

Onyx Pharmaceuticals (Nasdaq: ONXX)

$33.09

***

(26.43%)

$23.65-$61.18

TierOne (Nasdaq: TONE)

$15.17

****

(12.82%)

$13.77-$33.02

SI International (Nasdaq: SINT)

$23.55

***

(10.69%)

$23.13-$34.87

Radian Group (NYSE: RDN)

$7.53

*

(7.27%)

$5.44-$63.95

Verizon (NYSE: VZ)

$35.34

****

(6.58%)

$35.19-$46.24

Sources: The Wall Street Journal, Yahoo! Finance, Motley Fool CAPS.

Naughty?
Well, OK, we can't exactly call these stocks naughty. There are days when five-star winners and newsletter recommendations appear here (though not today).

But if you're an investor, you'll have plenty of bad days. The trick is to avoid dating -- or, worse, marrying -- your losers. That's why I listen when our 83,000-person-strong Motley Fool CAPS community of stock pickers contributes a poor rating or a negative pitch. You should, too. Here's today's list of the worst stocks in the world.

Worse
We begin with mortgage insurer Radian, which on Friday reported a $1.2 billion loss during 2007. Talk about awful.

But at least one analyst believes it could get worse, saying that Radian may be forced to raise fresh capital to remain afloat. That should surprise no one. Not even a week ago, peer MGIC Investment (NYSE: MTG) told investors that it would have to raise funds.

Worser
Next up is Onyx Pharmaceuticals, which, together with partner Bayer AG, halted trials of Nexavar, after an independent monitoring board said the lung cancer drug had no chance to succeed. Doesn't get much worse than that for a biotech.

Worst
But our winners are Verizon, AT&T (NYSE: T), and Deutsche Telekom's T-Mobile, all of which announced flat rates for unlimited domestic calling plans.

What's so bad about that? Nothing. It's the domino effect that troubles me. Verizon was first, announcing a $99.99 plan at 7:30 a.m. Eastern time. AT&T followed with a similar plan and pricing at 12:47 p.m. T-Mobile played the caboose on this fast train to nowhere with a copycat press release at 8 p.m.

It's as if all three telecom titans were lining up to face a drill sergeant. (Ten-hut!)

The all-you-can-eat plans imply that there's no difference among these three carries' offerings -- and, thereby, no discernible competitive advantage. So what do they do? Move in lockstep, just like the domestic airlines do when raising fares.

And that's worked out just dandy for airline investors, hasn't it? Buckle your seat belts, telecom investors.

Verizon, AT&T, and Deutsche Telekom, and their weak-kneed pricing practices ... Tuesday's worst stocks in the CAPS world.

Do you agree? Disagree? Let us know what you think by signing up for CAPS today. It's 100% free to participate.

I'll be back tomorrow with more stock horror stories.