Ah the infamous Lynel. The scourge of certain mountaintops or plains in The Legend of Zelda: Breath of the Wild is back in Hyrule Warriors, and while it isn't as difficult to defeat, Lynels are still very challenging.
You first meet the Lynel in the Mipha: The Zora Princess battle in the familiar realm of Zora's Domain, after rescuing four Zora captains and toppling some monsters. He's at the top of Ploymus Mountain, in roughly the same area as BOTW, although the layout is different and it's exclusively nighttime.
Make sure to upgrade your weapons before you face this ominous foe.
The Lynel is lightning fast and can overwhelm you with his attacks fairly quickly. The key is to keep a medium distance from him. When he charges, dodge to the side. He'll hit you if you dodge backward.
The Lynel also has a lunge attack. To avoid that, dodge either backward or forwards. If you time a dodge right, you'll get a chance to do a flurry attack, which will break down the Lynel's defense.
It can be intimidating when the Lynel charges at you, but using bombs will stun it, giving you a chance to counter.
Finally, be wary of the flame attack, which will set anything within a certain radius ablaze. Again, the key is dodging at the right moment. This is not an easy fight, and unfortunately, he's not the last boss of the area, but we'll cover that in another post.
This is a sight I saw quite a few times while trying to defeat the Lynel. Hopefully, you won't say the same thing after reading.