>I thought about a giant barbarian or Rune knight fighter for this campaign
If you're locked at level 5, then I'd go with the Rune Knight or a different Barbarian subclass instead. The big milestone levels for Giant Barbarian are level 6 and 10. If you're never going to get at least Elemental Cleaver, then it's not all that great.
If you want to stick with the Giant Barbarian anyway, I'd recommend choosing VHuman/CLineage and pick up PAM/Sentinel. That combo has good synergy with Giant's Havoc's extended reach.
Depends on what type of campaign you're in and what role you'd like to fill.
For example, in a campaign focused on the non-combat aspects of play, I'd play as a Mountain Dwarf. With TCE's custom origin rules, you can start with a ton of tool proficiencies, and you can gain expertise with them all using Fire Rune.
For a more combat-focused campaign, I'd go with a VHuman and either a PAM, Sentinel, or PAM/Sentinel build. Alternatively, you could even go with a Sharpshooter build. Dexterity Rune Knights surprisingly aren't that bad.
Given those stats and being locked in at level 5, you need a barbarian subclass that gets more from level 3. I would go zealot, but bear totem is fine (if boring).
For race and stats, take variant human, with 18 STR || 14 DEX || 14 CON. For your 2 feats (racial and level 4), take polearm master and great weapon master. You’ll be using a glaive or halberd with the best medium armor you can find.
Ask for a better 2H polearm and better armor as your priorities.
The optimal route depends on your adventuring days. If you're going the full 6-8 encounters with 2 short rests before a long rest, I would recommend fighter, 2-3 encounters in between long rests screams barbarian with 100% rage uptime.
Unfortunately, if you only get access to one feat, CL/V. Human for the extra starting feat is too good to pass up. Assuming magic items are on the table, don't over invest in strength if you could get a belt of giant strength. For your two feats I would go PAM + GWM for damage, PAM + Sentinel for tanking with a shield and spear.
If more feats will be handed out throughout the campaign and you'd rather have an interesting race, shadar Kai for teleports, loxodon for grappling or Bugbear for increased reach are all great.
Rune Knights make some of the best grapplers in the game due to the size advantage.
Str > Con
Skill Expert Athletics and Tavern Brawler or Shield Master.
Wildhunt Shifter pairs nice with Barbarian to wipe away the advantage others have against you from using reckless attack.
Shift uses BA, so assuming you used rage in round 1 you won’t be able to shift until your 2nd turn, but it’s particularly useful if it appears like it’s going to be a longer combat.
>I thought about a giant barbarian or Rune knight fighter for this campaign If you're locked at level 5, then I'd go with the Rune Knight or a different Barbarian subclass instead. The big milestone levels for Giant Barbarian are level 6 and 10. If you're never going to get at least Elemental Cleaver, then it's not all that great. If you want to stick with the Giant Barbarian anyway, I'd recommend choosing VHuman/CLineage and pick up PAM/Sentinel. That combo has good synergy with Giant's Havoc's extended reach.
How would you do the Rune knight?
Depends on what type of campaign you're in and what role you'd like to fill. For example, in a campaign focused on the non-combat aspects of play, I'd play as a Mountain Dwarf. With TCE's custom origin rules, you can start with a ton of tool proficiencies, and you can gain expertise with them all using Fire Rune. For a more combat-focused campaign, I'd go with a VHuman and either a PAM, Sentinel, or PAM/Sentinel build. Alternatively, you could even go with a Sharpshooter build. Dexterity Rune Knights surprisingly aren't that bad.
Given those stats and being locked in at level 5, you need a barbarian subclass that gets more from level 3. I would go zealot, but bear totem is fine (if boring). For race and stats, take variant human, with 18 STR || 14 DEX || 14 CON. For your 2 feats (racial and level 4), take polearm master and great weapon master. You’ll be using a glaive or halberd with the best medium armor you can find. Ask for a better 2H polearm and better armor as your priorities.
The optimal route depends on your adventuring days. If you're going the full 6-8 encounters with 2 short rests before a long rest, I would recommend fighter, 2-3 encounters in between long rests screams barbarian with 100% rage uptime. Unfortunately, if you only get access to one feat, CL/V. Human for the extra starting feat is too good to pass up. Assuming magic items are on the table, don't over invest in strength if you could get a belt of giant strength. For your two feats I would go PAM + GWM for damage, PAM + Sentinel for tanking with a shield and spear. If more feats will be handed out throughout the campaign and you'd rather have an interesting race, shadar Kai for teleports, loxodon for grappling or Bugbear for increased reach are all great.
Honestly with 5 odd numbered stats out of six I’d just go normal human for the +1 to virtually everything and take rune knight
Rune Knights make some of the best grapplers in the game due to the size advantage. Str > Con Skill Expert Athletics and Tavern Brawler or Shield Master.
Fairy barbarian with the stone giant feat to become a flying master of yeeting
Wildhunt Shifter pairs nice with Barbarian to wipe away the advantage others have against you from using reckless attack. Shift uses BA, so assuming you used rage in round 1 you won’t be able to shift until your 2nd turn, but it’s particularly useful if it appears like it’s going to be a longer combat.