The Witcher 3: Wild Hunt

This achievement is gained once you have defeated the Toad "Prince" boss in the sewers of Oxenfurt. This is unmissable.

The Toad Prince is a fairly difficult boss; it has fast attacks, with plenty of range and close combat capabilities. Preparation is vital: bring lots of healing items and thunderbolt. Also according to eurogamer.net it is vulnerable to Northern Wind, Golden Oriole, and Cursed Oil. Also, the Dragon's Dream and Grapeshot combo work effectively.

This can be done on any difficulty, all that changes is the length of the fight (because of the relative strength of the boss), so if you plan on doing this on Death March then make sure you are fully prepared for a long repetitive fight.

Follow these steps:

1. Place Yrden, preferably not too far from the boss (but not in range of its leap).

2. Dodge attacks until the Toad Prince makes its way over to you and steps in the trap, you can throw bombs if you wish.

3. Move towards the boss, applying thunderbolt as you approach.

4. Attack three times (from what I found, its stun is lifted after three hits, heavy or light. So you may as well do heavy, as it would do more damage overall).

5. Dodge away, healing if necessary.

6. Repeat.

It will be unsurprising if this takes a few tries; I personally found this more difficult than the final boss.

Thanks to Kahless Clone for the Dragon's Dream & Grapeshot combo.

Story related achievement and cannot be missed; assuming you don't break your TV or console.

You'll be given a Monster Contract at the beginning of the DLC requiring you to enter the Oxenfurt Sewers and fight a toad monster that has been slaughtering those citizens and soldiers alike who entered the bowels of Oxenfurt.

Now how to beat this thing. If you have enough healing items, buy more. If you have enough potions, buy more.

Toad only has a few attacks but they all deal considerable damage. He can shoot poisonous balls at you that cause where they landed to become toxic for a bit. If you're far away, it will stab at you with a sword like tongue. If you're close, it will use its tongue to whiplash you. And regardless of your placement it can hop and stomp all over you.

Here's the trick. Ignore everything Geralt says leading up to the encounter. You'll explore the sewers and he'll make mention that the monster isn't affected by fire. That's an absolute lie.

At the start of the battle just dodge, bob and weave until you get an idea of the toads attacks.

Once you're feeling comfortable, start bombarding the toad with Igni fire. Hit with fire, run away. Rinse and repeat. Heal as necessary and never let yourself get backed into a corner. Depending on how advanced your Igni tree is this can take anywhere from five to ten minutes if you plan your dodges well.

This solution works perfect for those who have either fully maxed out their Signs or have a full physical combat builds.

It takes some time, but it is doable and satisfying upon defeating it.