Upgrading 4.6.14 LTS Upgrade
After looking Civi log it seems that problem is with civicrm_uf_group.frontend_title field. I would suggest you to do incremental upgrade i.e

Upgrade CiviCRM to 4.6.x to 4.7.30
Upgrade CiviCRM to 4.7.31.


  On a separate note make sure you disable all the CiviCRM extension or
  wp plugin and also disable wp post or pages that have CiviCRM profile
  shortcode before upgrading.


HTH

Pradeep