Demonic Beast Akumu

Strategy

There are two ways on how to defeat this boss:

Pierce Team
Red Lostvayne Meliodas Team

Main factors of getting high points

Clearing speed - Points are deducted in proportion to the number of turns used. After the 7th turn, succeeding turns will deduct a significant amount of points to your total score.
Remaining HP - Additional points are added in proportion to the team’s remaining HP
Combat Class - Additional points are added in proportion to the team’s CC
Number of surviving heroes - Additional points are added in proportion to the team’s health status.
Skill effects
1. Infect
2. Cancel Stance
3. Detonate
4. Charge

There are 3 additional missions you can accomplish to get more points and these missions change every week.

Note that a strong AOE attacker is needed in this battle. That way you can still hit the boss despite the taunt effect of its Shield.

Make sure to eliminate the boss ASAP when his Sword and Shield is broken. Leaving him alone on the battlefield will activate a unique effect where the boss becomes invulnerable for 2 turns. Also, the boss increases its Attack-related stats every time an ally dies.

HP increase food is highly recommended.

Building your team

Here are a few tips to maximize your score and get all rewards:

Attacker

Heroes with strong AOE ultimate and/or Pierce effect is highly recommended.

Sustain

A hero who can heal or provide damage mitigation is highly recommended in harder difficulties. Make sure to cleanse and heal your team before finishing off the boss.