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.