Usually, when I play as Wigfrid in a server alone, before fighting any season giant, I make sure:
- I can deal at least 4000 damages with my equiped weapon (that's around 76% of a Battle Spear durability as Wigfrid; it would take around 60% of 2 regular Spear to take him down with characters who have normal damage multiplier, or 2 players with a regular Spear).
- I have 2 or 3 helms available in my inventory, just in case (or anything that gives at least 80% damage protection).
- I have at least 75% of my character's health (assuming you're not playing as Maxwell, since his health cap only at 75).
- I have some healing items (preferably Healing Salve), just in case.
Once I'm ready, I just rush in and attack.
During the fight:
- When you just started the fight, the Deerclops needs to hit you 3 times to freeze you. But if you already got frozen and he unfroze you by hitting you, the next hit will instantly freeze you.
- Everytime the Deerclops hit you, you'll notice your character will get a "pale" tone, which means they're "freezing". Upon being hit twice, run away until the pale colour fades away before charging again, this way the next hit you take won't freeze you.
- If you're playing with a friend, your friend should be standing on the opposite side of the Deerclops, this way you don't both get hit when he attacks.
- Keep hitting him until he's dead.
If fighting isn't a solution, when I hear a "warning sound" from the giants, I run as far as I can from my camp (if I have one).
Once the giant monster has spawned, I leave him on that part of the map, this way he won't respawn on subsequent season (e.g. a new Deerclops won't spawn in the next Winter, if the previous one wasn't killed). You just have to make sure that nobody approach that part of the map (consider it a quarantine area).