For this achievement, you must win at least 150 Head-to-Heads.
To do this, you must correctly predict an enemy monster’s attack and select the attack that will counter it.
Power beats Technical
Technical beats Speed
Speed beats Power
(There's a chart at the top of this page:
https://www.monsterhunter.com/stories/en-us/battle/)
For example, a Velocidrome in a non-enraged state will use a SPEED (BLUE) attack, so to win the Head-to-Head, you’ll want to use a TECHNICAL (GREEN) attack. Once you’ve won 150 Head-to-Heads, the achievement is yours!
Note, this only counts
your Head-to-Head victories,
not those of your companions. Before engaging in a battle with a monster, I was at 59 HtHs. Both me and Eleanor achieved one HtH each, however, after emerging from battle, my count had only gone up by 1.
Like many of these achievements, you can check your progress in your Ranger Records by pausing the game, navigating to “Ranger Files” (one tab to the right), and then selecting the Ranger Records dossier (the red one on the right).
Gambler's Shield is the second red meal, third along the second row.