The most selfish one letter word.....

"I"

Avoid It.

The most satisfying two-letter word.....

"We"

Use it.

The most poisonous three-letter word.....

"Ego"

Kill It.

The most used four-letter word.....

"Love"

Value it.

The most pleasing five-letter word.....

"Smile"

Keep it.

The fastest spreading six-letter word.....

"Rumour"

Ignore it.

The hardest working seven-letter word.....

"Success"

Achieve it.

The most enviable eight-letter word.....

"Jealousy"

Distant it.

The most powerful nine-letter word.....

"Knowledge"

Acquire it.

The most essential ten-letter word.....

"Confidence"

Trust it.

without the "I" you can't get any of the others