Lilina/Cecilia Infernal -
This one is pretty tough because there's less room than normal to manuever, and any opening turn puts you in range of multiple enemies. My setup:
-Tharja with Triangle Adept, Red Tomebreaker, Reposition, HP+3 seal
-Olwen with 48 Attack (+Atk, +1, Atk+1 seal, Death Blow 2, Eirika buff), Lancebreaker, Luna, Spur Res 3
-Eirika with Fortify Res seal
-I also had Spring Camilla but she ended up irrelevant, so a dancer would have been a better choice probably.
48 attack is key, however it is achieved. Olwen can barely ORKO both the lance pegasus knight and the added red mage (with a wolf tome) at this figure. She can also ORKO the brave lance cavalier. Reinhardt can pull this off much more easily, since Olwen's speed isn't necessary to this strategy. Tharja can be replaced by another red mage, one with more res would be nice (although most of those lack the raw power of Raudrblade).
1. Destroy the first wall, get in position for buffs etc.
2. Olwen ORKOs the lance peg.
3. Tharja repositions Olwen out of trouble, remains in danger of both Lilina and Cecilia.
4. Lilina and Ceclia both attack. With Triangle Adept, +6 res from Fortify/Spur, and +3 HP, Tharja can barely survive both. Red Tomebreaker is needed or Lilina's own Red Tomebreaker will wreck. Lilina barely survives, Cecilia does not. Meanwhile, the archer acts like an idiot and moves away to destroy the second wall.
5. Olwen ORKOs the lance knight, Tharja finishes Lilina.
6. Olwen ORKOs the red mage, reposition/etc. to avoid the archer.
7. Kill the archer with whoever.
Tharja's not one of my main squad but she seems to often end up as one of the centrepiece to my GHB strategies. (Berkut's battle had a similar situation where a powerful red TA mage was valuable.)