Here is the full list of all 18 Truxton 2 achievements.
Completed the first stage
Completed the first stage without assistance
First death of many achieved
Play a hundred games
Accumulate a thousand deaths
Completed the second stage
Completed the third stage
Completed the fourth stage
Completed the fifth stage
Completed the game.
Completed the second stage without assistance
Completed the third stage without assistance
Completed the fourth stage without assistance
Completed the fifth stage without assistance
Completed the game without assistance
One Credit Clear
One Credit Clear without assistance
Completed the game in Co-Op using one credit clear each player