Slitherine

Folks, i have been attempting to get the above achievement: use banzai charge to kill enemy unit, dealing at least 5 damage.

Problem is, i have tried two times, doing just that but the achievement won't hit. Each time, i reduce enemy unit to 5 strength, ensure enemy unit is not surrounded (i.e. it has space to retreat), activate banzai, eliminate unit. but achievement won't show.

I read in forum that the achievement may be bugged, i.e. damaging five points without killing unit may also get the achievement. Done that but nothing.

Am I missing something?

Thanks.

you actually have to destroy said unit while dealing at least 5 damage, one of the hardest achievements to get in my opinion, on par with getting an elite submarine considering you both have to destroy said unit and deal 5 damage to it during the attack. You might want to try softening up a unit in open terrain, preferably inferior to your own unit attacking. I would try doing this achievement against Philippine recruits in the Rising Sun campaign, or Chinese militia in the Morning Sun campaign.

In short - just use it on bunker/radar/... with >= 6 srt (5 str is not enough). It is nearly impossible to do this achievement not on static targets due to retreat mechanics.
As for 5-star sub - easy to do in American campaign. Just fire at all coast targets and keep it alive. Esp in last mission where you have 100 turns. I got 3d, 4th and 5th stars on last one

Just anihilated a Seabee unit dealing 5 points of damage. Didn't work. Was it so difficult to explain requirements clearly?

There is a bug in the game that causes players not to get the achievement: when you surround a mobile unit with 5 HP so it has no room to retreat and attack it with a banzai charge, the system thinks that you did less than 5 damage and the unit should retreat with some HP left, but the unit gets destroyed because it has nowhere to retreat.
To avoid this bug, chose a static unit, e.g., MG foxhole, radar station, fuel depot etc., or an mobile unit with 6 or more HP as a target. I chose an enemy airstrip. Because it is a static target, it would not retreat when I attack it with a banzai charge. Then I reduced its efficiency to 0 with strategic bombers (G3M Rikko), flanked it with 3 units, got a commander with a infantry attack trait with a range larger than 0 nearby, and chose an banzai infantry unit with 5 experience stars and 10 efficiency to do the attack so I would deal more damage. Last, I reduced the airstrip's HP to 6 before attacking with my banzai infantry. Ideally, the target should be in open terrain. But the airstrip was on difficult terrain, so I did less damage- 5 points of damage- a match with the combat prognosis. Yet, I got the achievement with the airstrip having 1 HP left. Thus there is another bug: you don't have to kill the unit on certain conditions.

I don't know about bugs or specifics on this achievement.
One important thing to keep in mind is that HP (hit points, health points, strength) is recorded on a 0-100 scale (technically at least 0-130 to account for difficulty level 5) but displayed on a 1-10 scale (again at least 1-13).
This generates rounding discrepancies (not errors) and a unit showing 5 HP may indeed only have 45 to 49 "basis point".
Hope this helps.