The giant rock golems and the 3 giants that chase you. Do I need more heart containers?
I didn't try defeating any of the world bosses until I had around 10 hearts.
However, you might be able to get by with defense boosting food, though you likely don't have the materials required for making good defense food yet.
The rock golems are easy. Climb on their back and attack the black ore until you get thrown off, rinse and repeat. They can't hit you at all while you're on their back. Expect to waste a few weapons doing this though. It seems like weapons that are normally good for mining (like the sledgehammer) are more effective against them. You could probably also use bombs.
As for the Hinox (the giant cyclops) I just swipe at their feet repeatedly until they go down. With a large amount of hearts what little damage you take from them sitting on you isn't much of an issue. However if you learn the timing you can dodge that and take them down without taking any damage, easily taking them down with only 5 hearts. I did beat my first Hinox relatively early in the game, they are among the easier world bosses.
Best stay as far away as possible from the Lynels though (I know you didn't mention them, just saying)
You can dodge their attacks fairly reliably (with the exception of the ones that carry the giant club, I haven't found a way to dodge that yet, it seems to have a higher range than my dodge range and even when I dodge perfectly and the Y button trigger shows up I still get hit a split second later), but you won't have the weapons needed for taking them down yet as they have a lot of HP.
At one point in the game you will need to get close to one but it's probably best just to use stealth to get what you need and get out of there without attracting its attention. You can kill them with relative ease once you have a few 30+ attack weapons. And preferably the Master Sword.