Warhammer: End Times - Vermintide

This is a tough achievement, but unlike others (stupid flipping Quarry event) the achievement is only invalidated if you take damage, not an ally.

My best recommendation is to only go for two people getting the achievement at a time (this is basically impossible to do solo as far as I can see, so you're going to need a party.) From the moment you hit the chain to start the boat ride until you step off it, the no-damage phase is in effect. The two people going for the achievement should be the Dwarf or Captain, with devastating blow and either balance or improved pommel on their shields. This will give you the maximum amount of blocking time, as well as enough range on your shield blows.

The other two players should ideally have potion shares and the no-damage bomb trinket so that you can chuck grenades without worrying about friendly fire. The witch is really not the hero for this, so I suggest elf and magehunter.

At the start of the boat event, make sure not to take any damage from the gunners or gas rats that may spawn on the shores. From now on, the two heroes going for the achievement should never stop blocking, save for possibly throwing extra bombs or potions to the other two players. Their goal is to position themselves at the two gang ramps so that when rats start jumping over, you can use devastating blow to either stagger them, or send some of them hurtling into the water, thinning the herd.

The other two players have the tough job, but since they're not worried about taking damage they can play fast and a little reckless. Time is of the essence; memorize the pattern for when enemy boats connect, and use potions to quickly sever the chains and stop the flow of reinforcements from that side. Ideally, everyone will have a speed or strength potion and bomb, and so during the few lulls the shield players can pass over supplies for the next round. If you're fast, this part is no big deal.

The next phase is to ferry the barrels. When this phase hits, have the shield players and everyone else retreat to the bow of the boat to prevent being surrounded, and prioritize storm rats. There will be no other specials spawning, so these guys are the only ones who can really ruin your day. If you need to clear the deck, chuck a bomb. Here's the trick; if you clear a wave totally, a new horn and new wave of reinforcements will arrive. Your goal instead is to thin their numbers, killing storm rats and then moving as a group towards the back of the boat to grab the barrels and chuck them over during the relative quiet. Two shield characters should be able to batter the enemies out of the way for the other players to ferry the barrels in safety. Don't get greedy; if you can't get two in at one time just fall back and reset your position, clear out the new black rats, and repeat.

On our attempts it occasionally happened that one of the guys shielding would take damage somehow, but we got a guaranteed one person getting the achievement each time rather than constantly failing at the boat point with no one getting anything (and if everyone's trying to avoid damage, you're likely not going to complete the mission, period.) Once the achievement has popped as you disembark to reach the other ship, you can finish up the mission for some XP and do it again, switching roles where needed.

The one that's needing the achievement can die before the rest goes onto the ship. The others finish the event and the one who died will get the achievement. Maybe that's a little bit easier than trying to avoid any hits on the boat.