Only in low dose. On higher dosage pure nicotine can cause acute poisoning just as with any substance ( caffeine, cocaine, alcohol... ).

Due to this I believe addiction itself has an inherently bad quality: Users with more tolerance could seek to increase their dosage, and they're more at risk of overdose.

We are not sure if it's not carcinogenic, or not having other long term damages. But only due to limited data, and does not mean it actually is safe.