The Belgian Congo was a miserable episode in history by all accounts - often considered one of most terrible examples of recent colonialism. Something to bear in mind next time next time you are chomping down on a delicious Belgian chocolate what with that industry being a direct legacy of colonialism.

The Spanish and Portuguese empires have much to be ashamed of too... Whether you should personally be ashamed for that is up to you.

Be ashamed or worried about your own sins. You're not responsible for the sins of your father's father's father.

There's a direct relationship between present dominance/power and the amount of guilt you're supposed to feel. That's basically how it works.

Spain and Portugal are no longer powerful nations, in either a military or economic sense (Portugal ranks behind Slovenia in GDP per capita for example).

If Italy were a super power today, they would be endlessly targeted for derision for their past connections to empire/s. It would be proclaimed that their present status was a direct result of abuses from the past and that they should feel guilty about it all.

Britain lost its empire and has persistently reduced in importance the last century, so they're rarely targeted for guilt regarding that (save for a few exceptions). It's a chapter in history books now, like so many former empires.

The Ottoman Empire? Long gone. Turkey isn't a major world power. As such, most of the world simply doesn't care about its terrible past.

The Spanish invaded, conquered, and enslaved most of South and Central America.

For the Portuguese, you probably have to look at Africa and Southeast Asia; I don't know much about them.