Just as 死了 can be used to intensify negative adjectives, 极了 (jíle) can be used to intensify positive adjectives.This is used in spoken, colloquial Chinese. 极 means "extreme" or "utmost", so using this grammar pattern takes your positive adjectives to the extreme!

Structure

It's as simple as using 极了 after the positive adjective.
Subject + Positive adjective + 极了

Note that this structure is a degree complement (called 程度补语 in Chinese)， and one of the few that you can use after the adjective and without adding a 得.
Examples

Tā hǎokàn jíle.
她 好看 极了。
She is very pretty.

Zhè ɡè píjiǔ hǎohē jíle.
这 个 啤酒 好喝 极了。
This beer is very tasty.

Nǐde zhōnɡwén hǎo jíle.
你的 中文 好 极了。
Your Chinese is very good!

Remember to add the 了, since this is sort of an exclamatory statement similar to 太好了. It would be incorrect without it.