It is a bit dependent on which ace, but generally speaking the best boss killer without competition is Eagle. The laser beam just melts through almost anything.
Of early planes Buzzsaw might be the strongest boss killer, but Katyusha, Greataxe, and Blaster are all good.
Flamer is good if you have the nerve to get up close.
Of later planes (level 90 and up), Sniper, Wraith, Hellfire, and Avenger all are good against bosses.
Patriot and Laserbite are not good, but no disaster. Especially Laserbite is so good in other aspects, that is worth equipping boss killing brobot.
Generally speaking avoid the following for boss fights: Blitzer (at least single/few target bosses like Red Queen, well handled it works fine against e.g. Doom, Gun Head, 100, 120), Sparrow, Phoenix, Defender, Dragon, Zapper, and Havoc.
This post is better if we can see the image of planes.
We hope to bring more graphics to this site before next game update!
Where is gambit abilities?
Laser Disrupting Field: Halves the damage done by enemy lasers.
Emergency Restoration Device: Once a battle nullifies a fatal hit, restoring armor to 20 %, and makes the plane invincible for 6 seconds.
Counter fire: After receiving 400 damage, protects the plane with a force field for 5 seconds and fires a barrage of missiles.
Emergency Restoration Device (rank SS): Once a battle nullifies a fatal hit, restoring armor to 40 %, and makes the plane invincible for 6 seconds.
https://hawkfreedomsquadron.com/planes/gambit/