3) Chris Sale
What do you know, another Atlanta Brave? Part of the reason why this list is dominated by Braves players has to do with the rest of the NL East being relatively inactive, but part of it also has to do with the players the Braves acquired being protypical Mets killers.
Guillorme and Kelenic had a bit of emotion behind them due to their Mets ties, but Sale feels like a Mets killer based on the pitcher he is. A funky left-hander who might not be as overpowering as he once was, but can still pitch well in big games.
Once again, the Mets struggled against left-handed pitching this past season, putting up a 96 WRC+ which was tied for 20th in the majors. While they hit for solid power against left-handed pitching, the Mets ranked 28th in the majors with a .237 batting average and tied for 24th with a .310 OBP. Not good!
While he's battled through injury issues with Boston and was not at the top of his game this past season, Sale in Atlanta feels like the next Charlie Morton. The Braves will inevitably find a way to rejuvenate his career and have him pitch particularly well against the Mets. It's possible that the Mets could own him the way they've owned Spencer Strider, but we'd have to see it to believe it.