Shadow Stantler

The Shadow bonus isn't strong enough to make Stantler worth using

Best PvE Offensive Moveset

• Tackle outperforms Zen Headbutt in neutral fights due to STAB, but can't be Super Effective vs anything.
• Wild Charge is the most powerful charge move available, but doesn't get STAB, and doesn't really synergize well either. 
• Stomp is an underwhelming move, but at least gets STAB at least and is a multi-bar move. 
• Megahorn doesn't have any use. 

Best PvE Defensive Moveset

• Zen Headbutt is best for defense due to its higher base power, and being Super Effective vs Stantler's weakness to Fighting-types. 
• Wild Charge hits hard as a 2-bar move, despite lacking STAB.
• Stomp isn't as strong even with STAB, but is harder to dodge. 
• Megahorn is bad on defense as a 1-bar move. 

Tackle and Zen Headbutt are both very bad moves, which are ultimately the biggest problems for Stantler. The former is better than the latter, and benefits from STAB. 

Stomp costs the least amount of energy, and benefits from STAB. Wild Charge is a powerful move and provides useful coverage, but is risky to use due to its self-debuff. Megahorn could be chosen if its coverage is needed, but demands more energy, and Bug-typing is typically not as valued. Return costs too much energy.