You need to do this by Category:
1) Trade acquisition that Avila was needlessly hyped over, but ended up as nothing but Hot Garbage: Dawel Lugo
2) Worst Starter on the market that Avila somehow felt was worth making a #3 starter. Who was, indeed, the worst starter on the market: Mike Pelfrey
3) Pitcher coming off an arm injury that seemed to be OK but also quite risky with recent underperformance compared to career norms in addition to the injury risk... That Spectacularly Blew Up in Avila's face: Jordan Zimmerman
4) Over-drafted "hitter" that had ZERO hit tool, some power, and a complete inability to field any position: Christin Stewart
5) Over-drafted "hitter" that had ZERO hit tool, some power, with a hit tool so bad no MLB, no ability to get to said power, Mendoza-like even in the MINORS, drafted in the top 2 rounds, and now every no-hit Tigers prospect is now compared to: Rey Rivera.
6) Awesome potential but injuries destroyed any chance to see the guy in MLB, immediately after we just traded our HOF Pitcher Justin Verlander for this key prospect: Franklyn Perez.
7) Below Replacement Level but we held onto him anyways because Avila couldn't find anyone better so he ended up with vastly more playing time as a Tiger than he EVER would have deserved with ANY other team in MLB: 4-way tie between Buck Farmer, Niko Goodrum, Christin Stewart, Harold Castro. (Feel free to expand this list to your heart's delight).
Or add as many additional categories... as needed.