The most selfish 1 letter word: I. Avoid it. 

The most satisfying 2 letter word: We. Use it. 

The most poisonous 3 letter word: Ego. Kill it. 

The most used 4 letter word: Love. Value it. 

The most pleasing 5 letter word: Smile. Keep it. 

The fastest spreading 6 letter word: Rumour. Ignore it. 

The hardest working 7 letter word: Success. Achieve it. 

The most enviable 8 letter word: Jealousy. Distance it. 

The most powerful 9 letter word: Knowledge. Acquire it. 

The most essential 10 letter word: Confidence. Trust it.