Learn Swedish: Vi lät explosionen renderas, och den blev hur bra som helst. - We had the explosion rendered, and it turned out as good as it gets.

The construction hur [adjective] som helst is an intensifier. It literally means "how [adjective] as whatsoever", but in Swedish it is used to take a quality to its absolute limit. In English, we would say "incredibly good", "as good as can be", or "as good as it gets". You can swap in almost any adjective or adverb to get this extreme effect.

Why is the verb låta (past tense lät) used to mean "had" in this sentence?

While låta commonly means "to let" or "to sound", here it functions as a causative verb, meaning someone caused an action to happen. Just like in English when you say "I had the car fixed", Swedish uses låta followed by an object and a passive verb to mean you "had [something] done".

Why does the verb renderas end in an -s here?

The -s at the end forms the s-passive of the infinitive rendera. Because the explosion isn't doing the rendering itself, it is having the action done to it. Following the causative verb lät, you need this passive infinitive to properly express that the explosion "was rendered".

Why do we use blev for "turned out" instead of another verb?